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Physics

New submissions

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New submissions for Tue, 20 Mar 18

[1]  arXiv:1803.06350 [pdf, other]
Title: Magnetic Prandtl number dependence of turbulence generated by chiral MHD dynamos
Comments: 18 pages, 10 figures, submitted to GAFD for the special issue "Recent Developments in Natural Dynamos"
Subjects: Fluid Dynamics (physics.flu-dyn); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); Plasma Physics (physics.plasm-ph)

An asymmetry in the number density of left- and right-handed fermions is known to give rise to a new term in the induction equation that can result in a small-scale instability. This is a microphysical effect characterised by a chiral chemical potential and is mathematically similar to the alpha effect, which is a turbulent or macrophysical effect. At high temperatures, when a chiral asymmetry can survive for long enough, these chiral MHD dynamos can amplify magnetic fields efficiently, which in turn drive turbulence via the Lorentz force. While it has been demonstrated in numerical simulations that chiral magnetically driven turbulence exists and modifies the evolution of the plasma, the details of this process remain unclear. The goal of this paper is to shed new light on the properties of chiral magnetically driven turbulence using numerical simulations with the Pencil Code. We explore the generation of turbulence for different initial conditions, including a variation of the initial chiral chemical potential and the magnetic Prandtl number, Pm. In particular, we determine the ratio of kinetic to magnetic energy, Upsilon^2, that can be reached in chiral magnetically driven turbulence. Within the parameter space explored in this study, Upsilon reaches a value of approximately 0.24-0.29 - independently of the initial chiral asymmetry and for Pm=1. Our simulations suggest, that Upsilon decreases as a power law when increasing Pm. While the exact scaling depends on the details of the fitting criteria and the Reynolds number regime, an approximate result of Upsilon(Pm)=0.3*Pm^{-0.2} is reported. Using the findings from our numerical simulations, we estimate the properties of chiral magnetically driven turbulence in the early Universe.

[2]  arXiv:1803.06358 [pdf, ps, other]
Title: Scaling of ion trapping in laser-driven relativistically transparent plasma
Subjects: Plasma Physics (physics.plasm-ph)

Ion trapping by ion wave breaking is investigated for laser-driven near-critical relativistically transparent plasma. Guided by three-dimensional particle-in-cell simulations, we study ion motion along the laser propagation direction within a 1D fluid model. The threshold for ion trapping is found, and the singular behaviour of longitudinal electric field, ion velocity, and ion density in the vicinity of the ion wave breaking point is derived analytically showing power-law distributions. The important result is that only a fraction of ions is trapped, different from the regime of hole boring. The number of trapped particles is determined and how it depends on target density for fixed laser intensity. Results are confirmed by the simulations.

[3]  arXiv:1803.06370 [pdf, other]
Title: First Calorimetric Measurement of Electron Capture in ${}^{193}$Pt with a Transition Edge Sensor
Comments: 17th International Workshop on Low Temperature Detectors
Subjects: Atomic Physics (physics.atom-ph); Instrumentation and Detectors (physics.ins-det)

The neutrino mass can be extracted from a high statistics, high resolution calorimetric spectrum of electron capture in ${}^{163}$Ho. In order to better understand the shape of the calorimetric electron capture spectrum, a second isotope was measured with a close to ideal absorber-source configuration. ${}^{193}$Pt was created by irradiating a ${}^{192}$Pt-enriched platinum foil in a nuclear reactor. This Pt-in-Pt absorber was designed to have a nearly ideal absorber-source configuration. The measured ${}^{193}$Pt calorimetric electron-capture spectrum provides an independent check on the corresponding theoretical calculations, which have thus far been compared only for ${}^{163}$Ho. The first experimental and theoretically-calculated spectra from this ${}^{193}$Pt-in-Pt absorber are presented and overlaid for preliminary comparison of theory with experiment.

[4]  arXiv:1803.06371 [pdf]
Title: Ludvig Lorenz (1867) on Light and Electricity
Authors: Helge Kragh
Comments: 8 pages
Subjects: History and Philosophy of Physics (physics.hist-ph)

Independent of Maxwell, in 1867 the Danish physicist L. V. Lorenz proposed a theory in which he identified light with electrical oscillations propagating in a very poor conductor. Lorenz's electrodynamic theory of light, which formally was equivalent to Maxwell's theory but physically quite different from it, was published in well-known journals in German and English but soon fell into oblivion. In 1867 Lorenz also published a paper on his new theory in a semi-popular Danish journal which has generally been overlooked. This other paper is here translated into English and provided with the necessary annotations.

[5]  arXiv:1803.06375 [pdf, other]
Title: Mobile phone records to feed activity-based travel demand models: MATSim for studying a cordon toll policy in Barcelona
Comments: 16 pages, 16 figures
Subjects: Physics and Society (physics.soc-ph); Social and Information Networks (cs.SI)

Activity-based models appeared as an answer to the limitations of the traditional trip-based and tour-based four-stage models. The fundamental assumption of activity-based models is that travel demand is originated from people performing their daily activities. This is why they include a consistent representation of time, of the persons and households, time-dependent routing, and microsimulation of travel demand and traffic. In spite of their potential to simulate traffic demand management policies, their practical application is still limited. One of the main reasons is that these models require a huge amount of very detailed input data hard to get with surveys. However, the pervasive use of mobile devices has brought a valuable new source of data. The work presented here has a twofold objective: first, to demonstrate the capability of mobile phone records to feed activity-based transport models, and, second, to assert the advantages of using activity-based models to estimate the effects of traffic demand management policies. Activity diaries for the metropolitan area of Barcelona are reconstructed from mobile phone records. This information is then employed as input for building a transport MATSim model of the city. The model calibration and validation process proves the quality of the activity diaries obtained. The possible impacts of a cordon toll policy applied to two different areas of the city and at different times of the day is then studied. Our results show the way in which the modal share is modified in each of the considered scenario. The possibility of evaluating the effects of the policy at both aggregated and traveller level, together with the ability of the model to capture policy impacts beyond the cordon toll area confirm the advantages of activity-based models for the evaluation of traffic demand management policies.

[6]  arXiv:1803.06378 [pdf, ps, other]
Title: Characterizing Ion Flows Across a Dipolarization Jet
Subjects: Space Physics (physics.space-ph); Plasma Physics (physics.plasm-ph)

The structure of dipolarization jets with finite width in the dawn-dusk direction relevant to magnetic reconnection in the Earth's magnetotail is explored with particle-in-cell simulations. We carry out Riemann simulations of the evolution of the jet in the dawn-dusk, north-south plane to investigate the dependence of the jet structure on the jet width in the dawn-dusk direction. We find that the magnetic field and Earth-directed ion flow structure depend on the dawn-dusk width. A reversal in the usual Hall magnetic field near the center of the current sheet on the dusk side of larger jets is observed. For small widths, the maximum velocity of the Earthward flow is significantly reduced below the theoretical limit of the upstream Alfv\'en speed. However, the ion flow speed approaches this limit once the width exceeds the ion Larmor radius based on the normal magnetic field, $B_z$.

[7]  arXiv:1803.06379 [pdf, other]
Title: Photon detector system performance in the DUNE 35-ton prototype liquid argon time projection chamber
Comments: 17 pages, 8 figures
Subjects: Instrumentation and Detectors (physics.ins-det); High Energy Physics - Experiment (hep-ex)

The 35-ton prototype for the Deep Underground Neutrino Experiment far detector was a single-phase liquid argon time projection chamber with an integrated photon detector system, all situated inside a membrane cryostat. The detector took cosmic-ray data for six weeks during the period of February 1, 2016 to March 12, 2016. The performance of the photon detection system was checked with these data. An installed photon detector was demonstrated to measure the arrival times of cosmic-ray muons with a resolution better than 32 ns, limited by the timing of the trigger system. A measurement of the timing resolution using closely-spaced calibration pulses yielded a resolution of 15 ns for pulses at a level of 6 photo-electrons. Scintillation light from cosmic-ray muons was observed to be attenuated with increasing distance with a characteristic length of $155 \pm 28$ cm.

[8]  arXiv:1803.06389 [pdf, other]
Title: Mechanistic Regimes of Vibronic Transport in a Heterodimer and the Design Principle of Incoherent Vibronic Transport in Phycobiliproteins
Subjects: Chemical Physics (physics.chem-ph)

Following the observation of coherent oscillations in non-linear spectra of photosynthetic pigment protein complexes, particularly phycobilliprotein such as PC645, coherent vibronic transport has been suggested as a design principle for novel light harvesting materials operating at room temperature. Vibronic transport between energetically remote pigments is coherent when the presence of a resonant vibration supports transient delocalization between the pair of electronic excited states. Here, we establish the mechanism of vibronic transport for a model heterodimer across a wide range of molecular parameter values. The resulting mechanistic map demonstrates that the molecular parameters of phycobiliproteins in fact support incoherent vibronic transport. This result points to an important design principle: incoherent vibronic transport is more efficient than a coherent mechanism when energetic disorder exceeds the coupling between the donor and vibrationally excited acceptor states. Finally, our results suggest that the role of coherent vibronic transport in pigment protein complexes should be reevaluated.

[9]  arXiv:1803.06399 [pdf]
Title: Generation of Electron Whistler Waves at the Mirror Mode Magnetic Holes: MMS Observations and PIC Simulation
Comments: 13 pages, 6 figures
Subjects: Space Physics (physics.space-ph)

The Magnetospheric Multiscale (MMS) mission has observed electron whistler waves at the center and at the edges of magnetic holes in the dayside magnetosheath. The magnetic holes are nonlinear mirror structures since their magnitude is anti-correlated with particle density. In this article, we examine the growth mechanisms of these whistler waves and their interaction with the host magnetic hole. In the observations, as magnetic holes develop and get deeper, an electron population gets trapped and develops a temperature anisotropy favorable for whistler waves to be generated. In addition, the decrease in magnetic field magnitude and the increase in density reduces the electron resonance energy, which promotes the electron cyclotron resonance. To investigate this process, we used an expanding box particle-in-cell simulations to produce the mirror instability, which then evolves into magnetic holes. The simulation shows that whistler waves can be generated at the center and edges of magnetic holes, which reproduces the primary features of the MMS observations. The simulation shows that the electron temperature anisotropy develops in the center of the magnetic hole once the mirror instability reaches its nonlinear stage of evolution. The plasma is then unstable to whistler waves at the minimum of the magnetic field structures. In the saturation regime of mirror instability, when magnetic holes are developed, the electron temperature anisotropy appears at the edges of the holes and electron distributions become more isotropic at the magnetic field minimum. At the edges, the expansion of magnetic holes decelerates the electrons which leads to temperature anisotropies.

[10]  arXiv:1803.06419 [pdf, other]
Title: Topological Wave-Guiding Near an Exceptional Point: Defect-Immune, Slow-Light, Loss-Immune Propagation
Subjects: Optics (physics.optics)

Electromagnetic waves propagating, at finite speeds, in conventional wave-guiding structures are reflected by discontinuities and decay in lossy regions. In this Letter, we drastically modify this typical guided-wave behavior by combining concepts from non-Hermitian physics and topological photonics. To this aim, we theoretically study, for the first time, the possibility of realizing an exceptional point between \emph{coupled topological modes in a non-Hermitian non-reciprocal waveguide}. Our proposed system is composed of oppositely-biased gyrotropic materials (e.g., biased plasmas or graphene layers) with a balanced loss/gain distribution. To study this complex wave-guiding problem, we put forward an exact analysis based on classical Green's function theory, and we illustrate the behavior of coupled topological modes and the nature of their non-Hermitian degeneracies. We find that, by operating near an exceptional point, we can realize anomalous topological wave propagation with, at the same time, low group-velocity, inherent immunity to back-scattering at discontinuities, and immunity to losses. These theoretical findings may open exciting research directions and stimulate further investigations of non-Hermitian topological waveguides to realize robust wave propagation in practical scenarios.

[11]  arXiv:1803.06421 [pdf, other]
Title: Uncertainties in permittivities computed from molecular dynamics simulations and temperature correction of dielectric properties of condensed polar systems
Comments: 10 pages, 5 figures and 2 tables
Subjects: Chemical Physics (physics.chem-ph)

A robust, simple and fast procedure for the calculation of uncertainties in relative static dielectric permittivity ($\varepsilon_s$) computed via molecular dynamics (MD) is proposed. It arises as a direct application of well founded statistical methods for auto-correlated variables. Also, in order to deal with the lack of experimental data about $\varepsilon_s$ and relaxation times ($\tau$) at different temperatures, a method for their prediction is suggested. It requires one experimental value and at least two MD simulations. In the case of relaxation times, a theoretical justification is provided.

[12]  arXiv:1803.06427 [pdf]
Title: Nonlinear nano-electromechanical lattices for high-frequency, tunable stress propagation
Subjects: Applied Physics (physics.app-ph)

Active manipulation of mechanical waves at high frequencies opens opportunities in heat management, radio-frequency (RF) signal processing, and quantum technologies. Nanoelectromechanical systems (NEMS) are appropriate platforms for developing these technologies, offering energy transducibility between different physical domains, for example, converting optical or electrical signals into mechanical vibrations and viceversa. Existing NEMS platforms, however, are mostly linear, passive, and not dynamically controllable. Here, we report the realization of active manipulation of frequency band dispersion in one-dimensional (1D) nonlinear nanoelectromechanical lattices (NEML) in the RF domain (10-30 MHz). Our NEML is comprised of a periodic arrangement of mechanically coupled free-standing nano-membranes, with circular clamped boundaries. This design forms a flexural phononic crystals with a well-defined band gaps, 1.8 MHz wide. The application a DC gate voltage creates voltage-dependent on-site potentials, which can significantly shift the frequency bands of the device. Dynamic modulation of the voltage triggers nonlinear effects, which induce the formation of phononic band gaps in the acoustic branch. These devices could be used in tunable filters, ultrasonic delay lines and transducers for implantable medical devices.

[13]  arXiv:1803.06429 [pdf, ps, other]
Title: How to automate a kinematic mount using a 3D printed Arduino-based system
Comments: 9 pages, 8 figures
Subjects: Instrumentation and Detectors (physics.ins-det)

We demonstrate a simple, flexible and cost-effective system to automatize most of the kinematic mounts available nowadays on the market. It combines 3D printed components, an Arduino board, stepper motors, and simple electronics. The system developed can control independently and simultaneously up to ten stepper motors using commands sent through the serial port, and it is suitable for applications where optical realignment using flat mirrors is required on a periodic basis.

[14]  arXiv:1803.06449 [pdf, other]
Title: Note: Variational Encoding of Protein Dynamics Benefits from Maximizing Latent Autocorrelation
Subjects: Chemical Physics (physics.chem-ph); Learning (cs.LG); Biological Physics (physics.bio-ph); Machine Learning (stat.ML)

As deep Variational Auto-Encoder (VAE) frameworks become more widely used for modeling biomolecular simulation data, we emphasize the capability of the VAE architecture to concurrently maximize the timescale of the latent space while inferring a reduced coordinate, which assists in finding slow processes as according to the variational approach to conformational dynamics. We additionally provide evidence that the VDE framework (Hern\'{a}ndez et al., 2017), which uses this autocorrelation loss along with a time-lagged reconstruction loss, obtains a variationally optimized latent coordinate in comparison with related loss functions. We thus recommend leveraging the autocorrelation of the latent space while training neural network models of biomolecular simulation data to better represent slow processes.

[15]  arXiv:1803.06450 [pdf, other]
Title: Measuring fluorescence by observing field quadrature noise
Subjects: Atomic Physics (physics.atom-ph)

We perform balanced homodyne detection of the electromagnetic field in a single-mode tapered optical nanofiber surrounded by rubidium atoms in a magneto-optical trap. Resonant fluorescence of atoms into the nanofiber mode manifests itself as increased quantum noise of the field quadratures. The autocorrelation function of the homodyne detector's output photocurrent exhibits exponential fall-off with a decay time constant of $26.3\pm 0.6$ ns, which is consistent with the theoretical expectation under our experimental conditions. To our knowledge, this is the first experiment in which fluorescence has been observed and measured by balanced optical homodyne detection.

[16]  arXiv:1803.06452 [pdf, ps, other]
Title: Spectral Estimation of Plasma Fluctuations II: Nonstationary Analysis of ELM Spectra
Comments: Figures missing
Journal-ref: Physics of Plasmas, Volume 1, Issue 3, March 1994, pp.501-514
Subjects: Plasma Physics (physics.plasm-ph)

Several analysis methods for nonstationary fluctuations are described and applied to the edge localized mode (ELM) instabilities of limiter H-mode plasmas. The microwave scattering diagnostic observes poloidal $k_{\theta}$ values of 3.3 cm$^{-1}$, averaged over a 20 cm region at the plasma edge.A short autoregressive filter enhances the nonstationary component of the plasma fluctuations by removing much of the background level of stationary fluctuations. Between ELMs, the spectrum predominantly consists of broad-banded 300-700 kHz fluctuations propagating in the electron diamagnetic drift direction, indicating the presence of a negative electric field near the plasma edge. The time-frequency spectrogram is computed with the multiple taper technique. By using the singular value decomposition of the spectrogram, it is shown that the spectrum during the ELM is broader and more symmetric than that of the stationary spectrum. The ELM period and the evolution of the spectrum between ELMs varies from discharge to discharge. For the discharge under consideration which has distinct ELMs with a 1 msec period, the spectrum has a maximum in the electron drift direction which relaxes to a near constant value %its characteristic shape in the first half millisecond after the end of the ELM and then grows slowly. In contrast, the level of the fluctuations in the ion drift direction increases exponentially by a factor of eight in the five milliseconds~after the ELM. High frequency precursors are found which occur one millisecond before the ELMs and propagate in the ion drift direction. These precursors are very short ($\sim 10 \mu$secs), coherent bursts, and they predict the occurrence of an ELM with a high success rate.

[17]  arXiv:1803.06462 [pdf, other]
Title: 500MHz resonant photodetector for high-frequency, high-quantum-effciency, low-noise homodyne measurement
Comments: 7 pages, 11 figures
Subjects: Applied Physics (physics.app-ph); Quantum Physics (quant-ph)

We design and demonstrate a resonant-type differential photodetector, for high-frequency, high-quantum-efficiency, low-noise quantum homodyne measurement at 500MHz optical sideband. By using a microwave monolithic amplifier and a discrete voltage buffer circuit, a low-noise voltage amplifier is realized and applied to our detector. 12dB of signal-to-noise ratio of the shot noise to the electric noise is obtained with 5mW of continuous-wave local oscillator at 860nm. We analyze the frequency response and the noise characteristics of a resonant photodetector, and the theoretical model agrees with the shot noise measurement.

[18]  arXiv:1803.06493 [pdf, ps, other]
Title: Actin filaments growing against an elastic membrane: Effect of membrane tension
Comments: 16 pages, 13 figures
Journal-ref: Physical Review E, vol. 97, 032408 (2018)
Subjects: Biological Physics (physics.bio-ph); Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech)

We study the force generation by a set of parallel actin filaments growing against an elastic membrane. The elastic membrane tries to stay flat and any deformation from this flat state, either caused by thermal fluctuations or due to protrusive polymerization force exerted by the filaments, costs energy. We study two lattice models to describe the membrane dynamics. In one case, the energy cost is assumed to be proportional to the absolute magnitude of the height gradient (gradient model) and in the other case it is proportional to the square of the height gradient (Gaussian model). For the gradient model we find that the membrane velocity is a non-monotonic function of the elastic constant $\mu$, and reaches a peak at $\mu=\mu^\ast$. For $\mu < \mu^\ast$ the system fails to reach a steady state and the membrane energy keeps increasing with time. For the Gaussian model, the system always reaches a steady state and the membrane velocity decreases monotonically with the elastic constant $\nu$ for all nonzero values of $\nu$. Multiple filaments give rise to protrusions at different regions of the membrane and the elasticity of the membrane induces an effective attraction between the two protrusions in the Gaussian model which causes the protrusions to merge and a single wide protrusion is present in the system. In both the models, the relative time-scale between the membrane and filament dynamics plays an important role in deciding whether the shape of elasticity-velocity curve is concave or convex. Our numerical simulations agree reasonably well with our analytical calculations.

[19]  arXiv:1803.06509 [pdf, ps, other]
Title: Explosive shock tube of xenon non-ideal plasma for proton radiography
Comments: 7 pages, 6 figures. To appear in the proceedings of XXXIII International Conference on Equations of State for Matter, 1-6, 2018, Elbrus, Kabardino-Balkaria, Russia
Subjects: Plasma Physics (physics.plasm-ph)

A high explosive shock tube of non-ideal gaseous plasma for proton radiography is described. The gas dynamic flow in the shock compressed xenon at initial pressure of 7 bar was investigated in the tube. The velocity of the shock wave in xenon and the associated particle velocity were measured by a high-speed rotating mirror streak camera. Experimental time-distance data was used for approximation of the velocities by exponential decay functions. The shock tube is intended for generation of non-ideal plasma of xenon at the pressure of 5-12 kbar, the density of 0.24-0.3 g/cm3 when the initial pressure is about 7 bar.

[20]  arXiv:1803.06526 [pdf]
Title: Titanium diboride ceramics for solar thermal absorbers
Journal-ref: Solar Energy Materials and Solar Cells, Volume 169 (2017) Pages 313-319
Subjects: Applied Physics (physics.app-ph); Materials Science (cond-mat.mtrl-sci)

Titanium diboride (TiB2) is a low-density refractory material belonging to the family of ultra-high temperature ceramics (UHTCs). This paper reports on the production and microstructural and optical characterization of nearly fully dense TiB2, with particular interest to its potential utilization as novel thermal solar absorber. Monolithic bulk samples are produced starting from elemental reactants by a two-step method consisting of the Self-propagating High-temperature Synthesis (SHS) followed by the Spark Plasma Sintering (SPS) of the resulting powders. The surface of obtained samples has-been characterized from the microstructural and topological points of view. The hemispherical reflectance spectrum has been measured from 0.3 to 15 um wavelength, to evaluate the potential of this material as solar absorber for future concentrating solar plants.

[21]  arXiv:1803.06532 [pdf, other]
Title: Highly charged ions: optical clocks and applications in fundamental physics
Comments: 53 pages, 16 figures, submitted to RMP
Subjects: Atomic Physics (physics.atom-ph)

Recent developments in frequency metrology and optical clocks have been based on electronic transitions in atoms and singly charged ions as references. These systems have enabled relative frequency uncertainties at a level of a few parts in $10^{-18}$. This accomplishment not only allows for extremely accurate time and frequency measurements, but also to probe our understanding of fundamental physics, such as variation of fundamental constants, violation of the local Lorentz invariance, and forces beyond the Standard Model of Physics. In addition, novel clocks are driving the development of sophisticated technical applications. Crucial for applications of clocks in fundamental physics are a high sensitivity to effects beyond the Standard Model and Einstein's Theory of Relativity and a small frequency uncertainty of the clock. Highly charged ions offer both. They have been proposed as highly accurate clocks, since they possess optical transitions which can be extremely narrow and less sensitive to external perturbations compared to current atomic clock species. The selection of highly charged ions in different charge states offers narrow transitions that are among the most sensitive ones for a change in the fine-structure constant and the electron-to-proton mass ratio, as well as other new physics effects. Recent advances in trapping and sympathetic cooling of highly charged ions will in the future enable high accuracy optical spectroscopy. Progress in calculating the properties of selected highly charged ions has allowed the evaluation of systematic shifts and the prediction of the sensitivity to the "new physics" effects. This article reviews the current status of theory and experiment in the field.

[22]  arXiv:1803.06546 [pdf, other]
Title: Microscale resolution thermal mapping using a flexible platform of patterned quantum sensors
Comments: 15 pages, 4 figures
Subjects: Applied Physics (physics.app-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Temperature sensors with micro- and nanoscale spatial resolution have long been explored for their potential to investigate the details of physical systems at an unprecedented scale. In particular, the rapid miniaturization of transistor technology, with the associated steep boost in power density, calls for sensors that accurately monitor heating distributions. Here, we report on a simple and scalable fabrication approach, based on directed self-assembly and transfer printing techniques, to construct arrays of nanodiamonds containing temperature sensitive fluorescent spin defects. The nanoparticles are embedded within a low thermal conductivity matrix that allows for repeated use on a wide range of systems with minimal spurious effects. Additionally, we demonstrate access to a wide spectrum of array parameters ranging from sparser single particle arrays to denser devices with approximately 100 % yield and stronger photoluminescence signal, ideal for temperature measurements. With these we experimentally reconstruct the temperature map of an operating coplanar waveguide to confirm the accuracy of these platforms.

[23]  arXiv:1803.06551 [pdf]
Title: A new elliptical-beam method based on time-domain thermoreflectance (TDTR) to measure the in-plane anisotropic thermal conductivity and its comparison with the beam-offset method
Comments: 35 pages, 12 figures, submitted to RSI
Subjects: Applied Physics (physics.app-ph)

Materials lacking in-plane symmetry are ubiquitous in a wide range of applications such as electronics, thermoelectrics, and high-temperature superconductors, in all of which the thermal properties of the materials play a critical part. However, very few experimental techniques can be used to measure in-plane anisotropic thermal conductivity. A beam-offset method based on time-domain thermoreflectance (TDTR) was previously proposed to measure in-plane anisotropic thermal conductivity. However, a detailed analysis of the beam-offset method is still lacking. Our analysis shows that uncertainties can be large if the laser spot size or the modulation frequency is not properly chosen. Here we propose an alternative approach based on TDTR to measure in-plane anisotropic thermal conductivity using a highly elliptical pump (heating) beam. The highly elliptical pump beam induces a quasi-one-dimensional temperature profile on the sample surface that has a fast decay along the short axis of the pump beam. The detected TDTR signal is exclusively sensitive to the in-plane thermal conductivity along the short axis of the elliptical beam. By conducting TDTR measurements as a function of delay time with the rotation of the elliptical pump beam to different orientations, the in-plane thermal conductivity tensor of the sample can be determined. In this work, we first conduct detailed signal sensitivity analyses for both techniques and provide guidelines in determining the optimal experimental conditions. We then compare the two techniques under their optimal experimental conditions by measuring the in-plane thermal conductivity tensor of a ZnO [11-20] sample. The accuracy and limitations of both methods are discussed.

[24]  arXiv:1803.06562 [pdf, other]
Title: Nanoscale domain patterns and a concept for an energy harvester
Comments: 8 pages, 9 figures
Journal-ref: Smart Materials and Structures, 25(10), 104001 (2016)
Subjects: Applied Physics (physics.app-ph)

The current work employs a phase-field model to test the stability of nanoscale periodic domain patterns, and to explore the application of one pattern in an energy harvester device. At first, the stability of several periodic domain patterns with in-plane polarizations is tested under stress-free and electric field-free conditions. It is found that simple domain patterns with stripe-like features are stable, while patterns with more complex domain configurations are typically unstable at the nanoscale. Upon identifying a stable domain pattern with suitable properties, a conceptual design of a thin film energy harvester device is explored. The harvester is modelled as a thin ferroelectric film bound to a substrate. In the initial state a periodic stripe domain pattern with zero net charge on the top electrode is modelled. On bending the substrate, a mechanical strain is induced in the film, causing polarized domains to undergo ferroelectric switching and thus generate electrical energy. The results demonstrate the working cycle of a conceptual energy harvester which, on operating at kHz frequencies, such as from vibrations in the environment, could produce an area power density of about 40W/m2.

[25]  arXiv:1803.06588 [pdf, ps, other]
Title: Cultural Evolution of Categorization
Comments: 17 pages
Subjects: Physics and Society (physics.soc-ph)

Categorization is a fundamental function of minds, with wide ranging implications for the rest of the cognitive system. In humans, categories are shared and communicated between minds, thus requiring explanations at the population level. In this paper, we discuss the current state of research on the cultural evolution of categorization. We begin by delineating key properties of categories in need of evolutionary explanation. We then review computational modeling and laboratory studies of category evolution, including their major insights and limitations. Finally, we discuss remaining challenges for understanding the cultural evolution of categorization.

[26]  arXiv:1803.06591 [pdf, ps, other]
Title: Recognizing number of communities and detecting community structures in complex networks
Subjects: Physics and Society (physics.soc-ph); Social and Information Networks (cs.SI)

Recognizing number of communities and detecting community structures of complex network are discussed in this paper. As a visual and feasible algorithm, block model has been successfully applied to detect community structures in complex network. In order to measure the quality of the block model, we first define an objective function WQ value. For obtaining block model B of a network, GSA algorithm is applied to optimize WQ with the help of random keys. After executing processes AO (Adding Ones) and RO (Removing Ones) on block model B, the number of communities of a network can be recognized distinctly. Furthermore, based on the advantage of block model that its sort order of nodes is in correspondence with sort order of communities, so a new fuzzy boundary algorithm for detecting community structures is proposed and successfully applied to some representative networks. Finally, experimental results demonstrate the feasibility of the proposed algorithm.

[27]  arXiv:1803.06611 [pdf, ps, other]
Title: Active Manipulation of Electromagnetically Induced Transparency in a Terahertz Hybrid Metamaterial
Authors: Tingting Liu
Subjects: Optics (physics.optics)

The metamaterial analogue of electromagnetically induced transparency (EIT) in terahertz (THz) regime holds fascinating prospects for filling the THz gap in various functional devices. In this paper, we propose a novel hybrid metamaterial to actively manipulate the resonance strength of EIT effect. By integrating a monolayer graphene into a THz metal metamaterial, an on-to-off modulation of the EIT transparency window is achieved under different Fermi levels of graphene. According to the classical two-particle model and the distributions of the electric field and surface charge density, the physical mechanism is attributable to the recombination effect of conductive graphene. This work reveals a novel manipulation mechanism of EIT resonance in the hybrid metamaterial and offers a new perspective towards designing THz functional devices.

[28]  arXiv:1803.06616 [pdf]
Title: Actively controlling the topological transition of dispersion based on electrically controllable metamaterials
Comments: 21 pages,8 figures
Subjects: Optics (physics.optics)

Topological transition of the iso-frequency contour (IFC) from a closed ellipsoid to an open hyperboloid, will provide unique capabilities for controlling the propagation of light. However, the ability to actively tune these effects remains elusive and the related experimental observations are highly desirable. Here, tunable electric IFC in periodic structure which is composed of graphene/dielectric multilayers is investigated by tuning the chemical potential of graphene layer. Specially, we present the actively controlled transportation in two kinds of anisotropic zero-index media containing PEC/PMC impurities. At last, by adding variable capacitance diodes into two-dimensional transmission-line system, we present the experimental demonstration of the actively controlled magnetic topological transition of dispersion based on electrically controllable metamaterials. With the increase of voltage, we measure the different emission patterns from a point source inside the structure and observe the phase-transition process of IFCs. The realization of actively tuned topological transition will opens up a new avenue in the dynamical control of metamaterials.

[29]  arXiv:1803.06638 [pdf, ps, other]
Title: Adaptive prior probabilities via optimization of risk and entropy
Comments: 15 pages, 3 figures
Subjects: Data Analysis, Statistics and Probability (physics.data-an); Statistical Mechanics (cond-mat.stat-mech); Computer Science and Game Theory (cs.GT)

An agent choosing between various actions tends to take the one with the lowest loss. But this choice is arguably too rigid (not adaptive) to be useful in complex situations, e.g. where exploration-exploitation trade-off is relevant, or in creative task solving. Here we study an agent that -- given a certain average utility invested into adaptation -- chooses his actions via probabilities obtained through optimizing the entropy. As we argue, entropy minimization corresponds to a risk-averse agent, whereas a risk-seeking agent will maximize the entropy. The entropy minimization can (under certain conditions) recover the epsilon-greedy probabilities known in reinforced learning. We show that the entropy minimization -- in contrast to its maximization -- leads to rudimentary forms of intelligent behavior: (i) the agent accounts for extreme events, especially when he did not invest much into adaptation. (ii) He chooses the action related to lesser loss (lesser of two evils) when confronted with two actions with comparable losses. (iii) The agent is subject to effects similar to cognitive dissonance and frustration. Neither of these features are shown by the risk-seeking agent whose probabilities are given by the maximum entropy. Mathematically, the difference between entropy maximization versus its minimization corresponds with maximizing a convex function (in a convex domain, i.e.convex programming) versus minimizing it (concave programming).

[30]  arXiv:1803.06648 [pdf, other]
Title: Charge migration mechanisms in the DNA at finite temperature revisited; from quasi-ballistic to subdiffusive transport
Subjects: Biological Physics (physics.bio-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Various charge migration mechanisms in the DNA are studied within the framework of the Peyrard-Bishop-Holstein model which has been widely used to address charge dynamics in this macromolecule. To analyze these mechanisms we consider characteristic size and time scales of the fluctuations of the electronic and vibrational subsystems. It is shown, in particular, that due to substantial differences in these timescales polaron formation is unlikely within a broad range of temperatures. We demonstrate that at low temperatures electronic transport can be quasi-ballistic. For high temperatures, we propose an alternative to polaronic charge migration mechanism: the fluctuation-assisted one, in which the electron dynamics is governed by relatively slow fluctuations of the vibrational subsystem. We argue also that the discussed methods and mechanisms can be relevant for other organic macromolecular systems, such as conjugated polymers and molecular aggregates.

[31]  arXiv:1803.06658 [pdf]
Title: Temperature dependent dynamics in water-ethanol liquid mixtures
Subjects: Chemical Physics (physics.chem-ph); Soft Condensed Matter (cond-mat.soft)

Temperature dependent hydrogen bond energetics and dynamical features, such as the diffusion coefficient and reorientational times, have been determined for ethanol-water mixtures with 10, 20 and 30 mol % of ethanol. Concerning pairwise interaction energies between molecules, it is found that water-water interactions become stronger, while ethanol-ethanol ones become significantly weaker in the mixtures than the corresponding values characteristic to the pure substances. Concerning the diffusion processes, for all concentrations the activation barrier of water and ethanol molecule become very similar to each other. Reorientation motions of water and ethanol become slower as ethanol concentration is increasing. Characteristic reorientational times of water in the mixtures are substantially longer than these values in the pure substance. On the other hand, this change for ethanol is only moderate. The reorientation motions of water (especially the ones related to the H-bonded interaction) become very similar for those of ethanol in the mixtures.

[32]  arXiv:1803.06660 [pdf]
Title: Temperature dependent network stability in simple alcohols and pure water: the evolution of Laplace spectra
Subjects: Chemical Physics (physics.chem-ph)

A number of computer-generated models of water, methanol and ethanol are considered at room temperature and ambient pressure, and also as a function of temperature (for water and ethanol), and the potential model (for water only). The Laplace matrices are determined, and various characteristics of this, such as eigenvalues and eigenvectors, and the corresponding Laplace spectra are calculated. It is revealed how the width of the spectral gap in the Laplace matrix of H-bonded networks may be applied for characterising the stability of the network. A novel method for detecting the presence percolated network in these systems is also introduced.

[33]  arXiv:1803.06663 [pdf, other]
Title: Direct Measurement of Focusing Fields in Active Plasma Lenses
Comments: 13 pages, 6 Figures
Subjects: Accelerator Physics (physics.acc-ph)

Active plasma lenses have the potential to enable broad-ranging applications of plasma-based accelerators owing to their compact design and radially symmetric kT/m-level focusing fields, facilitating beam-quality preservation and compact beam transport. We report on the direct measurement of magnetic field gradients in active plasma lenses and demonstrate their impact on the emittance of a charged particle beam. This is made possible by the use of a well-characterized electron beam with 1.4mmmrad normalized emittance from a conventional accelerator. Field gradients of up to 823T/m are investigated. The observed emittance evolution is supported by numerical simulations, which demonstrate the conservation of the core beam emittance in such a plasma lens setup.

[34]  arXiv:1803.06693 [pdf, other]
Title: Persistent incomplete mixing in reactive flows
Subjects: Fluid Dynamics (physics.flu-dyn)

We present an effective stochastic advection-diffusion-reaction (SADR) model that explains incomplete mixing typically observed in transport with bimolecular reactions. Unlike traditional advection-dispersion-reaction models, the SADR model describes mechanical and diffusive mixing as two separate processes. In the SADR model, mechanical mixing is driven by random advective velocity with the variance given by the coefficient of mechanical dispersion. The diffusive mixing is modeled as a Fickian diffusion with the effective diffusion coefficient. We demonstrate that the sum of the two coefficients is equal to the dispersion coefficients, but only the effective diffusion coefficient contributes to the mixing-controlled reactions, indicating that such systems do not get fully mixed at the Representative Elementary Volume scale where the deterministic equations and dispersion coefficient are defined. We use the experimental results of Gramling et al. \cite{Gramling} to show that for transport and bimolecular reactions in porous media, the SADR model is significantly more accurate than the traditional dispersion model, which overestimates the concentration of the reaction product by as much as 60\%.

[35]  arXiv:1803.06696 [pdf, other]
Title: Studies of a scheme for Low EMittance Muon Accelerator with production from positrons on target
Comments: submitted to Physical Review Accelerators and Beams
Subjects: Accelerator Physics (physics.acc-ph)

A study of a new scheme to produce very low emittance muon beams using a positron beam of about 45 GeV interacting on electrons on target is presented. One of the innovative topics to be investigated is the behaviour of the positron beam stored in a low emittance ring with a thin target, that is directly inserted in the ring chamber to produce muons. Muons can be immediately collected at the exit of the target and transported to two mu+ and mu- accumulator rings and then accelerated and injected in muon collider rings. We focus in this paper on the simulation of the e+ beam interacting with the target, the effect of the target on the 6-D phase space and the optimization of the e+ ring design to maximize the energy acceptance. We will investigate the performances of this scheme, ring plus target system, comparing different multi-turn simulations. A preliminary review of the full scheme parameters is discussed in view of the results obtained on the ring plus target system. In addition, a first acceleration scheme is presented together with a possible 14 TeV collider layout.

[36]  arXiv:1803.06714 [pdf, other]
Title: Mathematics for cryo-electron microscopy
Authors: Amit Singer
Comments: Proceedings of the International Congress of Mathematicians 2018
Subjects: Computational Physics (physics.comp-ph); History and Overview (math.HO)

Single-particle cryo-electron microscopy (cryo-EM) has recently joined X-ray crystallography and NMR spectroscopy as a high-resolution structural method for biological macromolecules. Cryo-EM was selected by Nature Methods as Method of the Year 2015, large scale investments in cryo-EM facilities are being made all over the world, and the Nobel Prize in Chemistry 2017 was awarded to Jacques Dubochet, Joachim Frank and Richard Henderson "for developing cryo-electron microscopy for the high-resolution structure determination of biomolecules in solution". This paper focuses on the mathematical principles underlying existing algorithms for structure determination using single particle cryo-EM.

[37]  arXiv:1803.06723 [pdf, other]
Title: Universality in statistics of Stokes flow over no-slip wall with random roughness
Subjects: Fluid Dynamics (physics.flu-dyn)

Stochastic roughness is widespread feature of natural surfaces and is an inherent by-product of most fabrication techniques. In view of rapid development of microfluidics, the important question is how this inevitable evil affects the low-Reynolds flows which are common for micro-devices. Moreover, one could potentially turn the flaw into a virtue and control the flow properties by means of specially "tuned" random roughness. In this paper we investigate theoretically the statistics of fluctuations in fluid velocity produced by the waviness irregularities at the surface of a no-slip wall. Particular emphasis is laid on the issue of the universality of our findings.

[38]  arXiv:1803.06748 [pdf]
Title: Optically resolving the dynamic walking of a plasmonic walker couple
Comments: 4 figures
Journal-ref: Nano Letters 15, 8392 (2015)
Subjects: Biological Physics (physics.bio-ph)

Deterministic placement and dynamic manipulation of individual plasmonic nanoparticles with nanoscale precision feature an important step towards active nanoplasmonic devices with prescribed levels of performance and functionalities at optical frequencies. In this Letter, we demonstrate a plasmonic walker couple system, in which two gold nanorod walkers can independently or simultaneously perform stepwise walking powered by DNA hybridization along the same DNA origami track. We utilize optical spectroscopy to resolve such dynamic walking with nanoscale steps well below the optical diffraction limit. We also show that the number of walkers and the optical response of the system can be correlated. Our studies exemplify the power of plasmonics, when integrated with DNA nanotechnology for realization of advanced artificial nanomachinery with tailored optical functionalities.

[39]  arXiv:1803.06751 [pdf]
Title: Plasmonic Toroidal Metamolecules Assembled by DNA Origami
Comments: 4 figures
Journal-ref: J. Am. Chem. Soc. 138, 5495 (2016)
Subjects: Biological Physics (physics.bio-ph); Soft Condensed Matter (cond-mat.soft)

We demonstrate hierarchical assembly of plasmonic toroidal metamolecules, which exhibit tailored optical activity in the visible spectral range. Each metamolecule consists of four identical origami-templated helical building blocks. Such toroidal metamolecules show stronger chiroptical response than monomers and dimers of the helical building blocks. Enantiomers of the plasmonic structures yield opposite circular dichroism spectra. The experimental results agree well with the theoretical simulations. We also demonstrate that given the circular symmetry of the structures, distinct chiroptical response along their axial orientation can be uncovered via simple spin-coating of the metamolecules on substrates. Our work provides a new strategy to create plasmonic chiral platforms with sophisticated nanoscale architectures for potential applications such as chiral sensing using chemically-based assembly systems.

[40]  arXiv:1803.06753 [pdf]
Title: DNA nanotechnology-enabled chiral plasmonics: from static to dynamic
Comments: 7 figures
Journal-ref: Acc. Chem. Res. 50, 2906 (2017)
Subjects: Biological Physics (physics.bio-ph); Soft Condensed Matter (cond-mat.soft)

In this Account, we discuss a variety of static and dynamic chiral plasmonic nanostructures enabled by DNA nanotechnology. In the category of static plasmonic systems, we first show chiral plasmonic nanostructures based on spherical AuNPs, including plasmonic helices, toroids, and tetramers. To enhance the CD responses, anisotropic gold nanorods with larger extinction coefficients are utilized to create chiral plasmonic crosses and helical superstructures. Next, we highlight the inevitable evolution from static to dynamic plasmonic systems along with the fast development of this interdisciplinary field. Several dynamic plasmonic systems are reviewed according to their working mechanisms.

[41]  arXiv:1803.06770 [pdf, ps, other]
Title: Kepler's laws without calculus
Authors: William G Unruh
Subjects: History and Philosophy of Physics (physics.hist-ph); Popular Physics (physics.pop-ph)

Kepler's laws are derived from the inverse square law without the use of calculus and are simplified over previous such derivations.

[42]  arXiv:1803.06821 [pdf, other]
Title: Development of co-located ${}^{129}$Xe and ${}^{131}$Xe nuclear spin masers with external feedback scheme
Comments: 8 pages, 5 figures
Journal-ref: Phys. Lett. A 382, 588-594 (2018)
Subjects: Atomic Physics (physics.atom-ph)

We report on the operation of co-located ${}^{129}$Xe and ${}^{131}$Xe nuclear spin masers with an external feedback scheme, and discuss the use of ${}^{131}$Xe as a comagnetometer in measurements of the ${}^{129}$Xe spin precession frequency. By applying a correction based on the observed change in the ${}^{131}$Xe frequency, the frequency instability due to magnetic field and cell temperature drifts are eliminated by two orders of magnitude. The frequency precision of 6.2 $\mu$Hz is obtained for a 10$^4$ s averaging time, suggesting the possibility of future improvement to $\approx$ 1 nHz by improving the signal-to-noise ratio of the observation.

[43]  arXiv:1803.06856 [pdf, other]
Title: Ultrafast Photodynamics of Glucose
Journal-ref: J. Phys. Chem. B 2018, 122, 19-27
Subjects: Chemical Physics (physics.chem-ph)

We have investigated the photodynamics of $\beta$-D-glucose employing our field-induced surface hopping method (FISH), which allows us to simulate the coupled electron-nuclear dynamics, including explicitly nonadiabatic effects and light-induced excitation. Our results reveal that from the initially populated S$_{1}$ and S$_{2}$ states, glucose returns nonradiatively to the ground state within about 200 fs. This takes place mainly via conical intersections (CIs) whose geometries in most cases involve the elongation of a single O-H bond, while in some instances ring-opening due to dissociation of a C-O bond is observed. Experimentally, excitation to a distinct excited electronic state is improbable due to the presence of a dense manifold of states bearing similar oscillator strengths. Our FISH simulations explicitly including a UV laser pulse of 6.43 eV photon energy reveals that after initial excitation the population is almost equally spread over several close-lying electronic states. This is followed by a fast nonradiative decay on the time scale of 100-200 fs, with the final return to the ground state proceeding via the S$_{1}$ state through the same types of CIs as observed in the field-free simulations.

[44]  arXiv:1803.06860 [pdf, other]
Title: Combined readout of a triple-GEM detector
Comments: 8 pages, 8 figures
Subjects: Instrumentation and Detectors (physics.ins-det); High Energy Physics - Experiment (hep-ex)

Optical readout of GEM based devices by means of high granularity and low noise CMOS sensors allows to obtain very interesting tracking performance. Space resolution of the order of tens of $\mu$m were measured on the GEM plane along with an energy resolution of 20%$\div$30%. The main limitation of CMOS sensors is represented by their poor information about time structure of the event. In this paper, the use of a concurrent light readout by means of a suitable photomultiplier and the acquisition of the electric signal induced on the GEM electrode are exploited to provide the necessary timing informations. The analysis of the PMT waveform allows a 3D reconstruction of each single clusters with a resolution on z of 100 $\mu$m. Moreover, from the PMT signals it is possible to obtain a fast reconstruction of the energy released within the detector with a resolution of the order of 25% even in the tens of keV range useful, for example, for triggering purpose.

[45]  arXiv:1803.06861 [pdf, ps, other]
Title: Analytical and numerical study of the non-linear noisy voter model on complex networks
Subjects: Physics and Society (physics.soc-ph); Statistical Mechanics (cond-mat.stat-mech)

We study the noisy voter model using a specific non-linear dependence of the rates that takes into account collective interaction between individuals. The resulting model is solved exactly under the all-to-all coupling configuration and approximately in some random networks environments. In the all-to-all setup we find that the non-linear interactions induce "bona fide" phase transitions that, contrarily to the linear version of the model, survive in the thermodynamic limit. The main effect of the complex network is to shift the transition lines and modify the finite-size dependence, a modification that can be captured with the introduction of an effective system size that decreases with the degree heterogeneity of the network. A non-trivial finite-size dependence of the moments of the probability distribution is derived from our treatment, nevertheless mean-field exponents are obtained in the thermodynamic limit. These theoretical predictions are well confirmed by numerical simulations of the stochastic process.

[46]  arXiv:1803.06868 [pdf, other]
Title: Generation of ten kilotesla longitudinal magnetic fields in ultraintense laser-solenoid target interactions
Comments: 5 pages, 4 figures
Subjects: Plasma Physics (physics.plasm-ph); Optics (physics.optics)

Production of the huge longitudinal magnetic fields by using an ultraintense laser pulse irradiating a solenoid target is considered. Through three-dimensional particle-in-cell simulations, it is shown that the longitudinal magnetic field up to ten kilotesla can be observed in the ultraintense laser-solenoid target interactions. The finding is associated with both fast and return electron currents in the solenoid target. The huge longitudinal magnetic field is of interest for a number of important applications, which include controlling the divergence of laser-driven energetic particles for medical treatment, fast-ignition in inertial fusion, etc., as an example, the well focused and confined directional electron beams are realized by using the solenoid target.

[47]  arXiv:1803.06880 [pdf, other]
Title: Scaling of energy amplification in viscoelastic channel and Couette flow
Comments: 40 pages, 10 figures, the material was partially presented at 2015 APS-DFD meeting, this manuscript was never submitted to a journal
Subjects: Fluid Dynamics (physics.flu-dyn); Computational Physics (physics.comp-ph)

The linear amplification of disturbances is critical in setting up transition scenarios in viscoelastic channel and Couette flow, and may also play an important role when such flows are fully turbulent. As such, it is of interest to assess how this amplification, defined as the steady-state variance maintained under Gaussian white noise forcing, scales with the main nondimensional parameters: the Reynolds ($Re$) and Weissenberg ($Wi$) numbers. This scaling is derived analytically in the two limits of strong and weak elasticity for when the forcing is streamwise-constant. The latter is the relevant forcing for capturing the overall behaviour because it was previously shown to have the dominant contribution to amplification. The final expressions show that for weak elasticity the scaling retains a form similar to the well-known O($Re^3$) relationship with an added elastic correction. For strong elasticity, however, the scaling is O($Wi^3$) with a viscous correction. The key factor leading to such a mirroring in the scaling is the introduction of forcing in the polymer stress. The results demonstrate that energy amplification in a viscoelastic flow can be very sensitive to the model parameters even at low $Re$. They also suggest that energy amplification can be significantly increased by forcing the polymer stress, thereby opening up possibilities such as flow control using systematically designed polymer stress perturbations.

[48]  arXiv:1803.06889 [pdf, other]
Title: Terahertz emission from laser-driven gas-plasmas: a plasmonic point of view
Subjects: Optics (physics.optics); Plasma Physics (physics.plasm-ph)

We investigate terahertz generation in two-color laser-induced gas plasmas. Resonances attributed to plasmonic effects are shown to broaden the emission spectra significantly, when electrons are excited along a direction where the plasma size is smaller than the plasma wavelength. We demonstrate that such resonances can be turned on and off by changing the polarization properties of elliptically-shaped driving laser-pulses. Both 3D Maxwell consistent simulations and experimental results confirm that a significant THz pulse shortening and spectral broadening can be achieved by exploiting the transverse driving laser-beam shape as an additional degree of freedom.

[49]  arXiv:1803.06900 [pdf, other]
Title: Analytical Impedance Models for Very Short Bunches
Authors: Igor Zagorodnov
Comments: 24 pages, 11 figures
Subjects: Accelerator Physics (physics.acc-ph)

We discuss several analytical models for impedances of very short bunches. The approximate analytical models are compared with direct solution of Maxwells equations.

[50]  arXiv:1803.06916 [pdf]
Title: Simulating the future urban growth in Xiongan New Area: a upcoming big city in China
Authors: Xun Liang
Subjects: Physics and Society (physics.soc-ph); Artificial Intelligence (cs.AI); Computers and Society (cs.CY)

China made the announement to create the Xiongan New Area in Hebei in April 1,2017. Thus a new magacity about 110km south west of Beijing will emerge. Xiongan New Area is of great practial significant and historical significant for transferring Beijing's non-capital function. Simulating the urban dynamics in Xiongan New Area can help planners to decide where to build the new urban and further manage the future urban growth. However, only a little research focus on the future urban development in Xiongan New Area. In addition, previous models are unable to simulate the urban dynamics in Xiongan New Area. Because there are no original high density urbna for these models to learn the transition rules.In this study, we proposed a C-FLUS model to solve such problems. This framework was implemented by coupling a modified Cellular automata(CA). An elaborately designed random planted seeds machanism based on local maximums is addressed in the CA model to better simulate the occurrence of the new urban. Through an analysis of the current driving forces, the C-FLUS can detect the potential start zone and simulate the urban development under different scenarios in Xiongan New Area. Our study shows that the new urban is most likely to occur in northwest of Xiongxian, and it will rapidly extend to Rongcheng and Anxin until almost cover the northern part of Xiongan New Area. Moreover, the method can help planners to evaluate the impact of urban expansion in Xiongan New Area.

[51]  arXiv:1803.06935 [pdf]
Title: Mathematical Analysis of Anthropogenic Signatures: The Great Deceleration
Authors: Ron W. Nielsen
Comments: 30 pages, 31 figures, 2 tables, 8991 words
Subjects: Physics and Society (physics.soc-ph); Populations and Evolution (q-bio.PE)

Distributions of anthropogenic signatures (impacts and activities) are mathematically analysed. The aim is to understand the Anthropocene and to see whether anthropogenic signatures could be used to determine its beginning. A total of 23 signatures were analysed and results are presented in 31 diagrams. Some of these signatures contain undistinguishable natural component but most of them are of purely anthropogenic origin. Great care was taken to identify abrupt accelerations, which could be used to determine the beginning of the Anthropocene. Results of the analysis can be summarised in three conclusions. 1. Anthropogenic signatures cannot be used to determine the beginning of the Anthropocene. 2. There was no abrupt Great Acceleration around 1950 or around any other time. 3. Anthropogenic signatures are characterised by the Great Deceleration in the second half of the 20th century. The Great Deceleration indicates a gradual progress towards a sustainable future.

[52]  arXiv:1803.06940 [pdf]
Title: The ECMWF Ensemble Prediction System: Looking Back (more than) 25 Years and Projecting Forward 25 Years
Authors: Tim Palmer
Comments: Submitted to Special Issue of the Quarterly Journal of the Royal Meteorological Society: 25 years of ensemble prediction
Subjects: Atmospheric and Oceanic Physics (physics.ao-ph)

This paper has been written to mark 25 years of operational medium-range ensemble forecasting. The origins of the ECMWF Ensemble Prediction System are outlined, including the development of the precursor real-time Met Office monthly ensemble forecast system. In particular, the reasons for the development of singular vectors and stochastic physics - particular features of the ECMWF Ensemble Prediction System - are discussed. The author speculates about the development and use of ensemble prediction in the next 25 years.

[53]  arXiv:1803.06950 [pdf, other]
Title: Study of point- and cluster-defects in radiation-damaged silicon
Comments: 13 pages, 12 figures, 4 tables
Subjects: Instrumentation and Detectors (physics.ins-det); Materials Science (cond-mat.mtrl-sci)

Non-ionising energy loss of radiation produces point defects and defect clusters in silicon, which result in a signifcant degradation of sensor performance. In this contribution results from TSC (Thermally Stimulated Current) defect spectroscopy for silicon pad diodes irradiated by electrons to fluences of a few $10^{14}$ cm$^{-2}$ and energies between 3.5 and 27 MeV for isochronal annealing between 80 and 280{\deg}C, are presented. A method based on SRH (Shockley-Read-Hall) statistics is introduced, which assumes that the ionisation energy of the defects in a cluster depends on the fraction of occupied traps. The dfference of ionisation energy of an isolated point defect and a fully occupied cluster, $\Delta E_a$, is extracted from the TSC data.
For the VOi (vacancy-oxygen interstitial) defect $\Delta E_a = 0$ is found, which cofirms that it is a point defect, and validates the method for point defects. For clusters made of deep acceptors the $\Delta E_a$ values for different defects are determined after annealing at 80{\deg}C as a function of electron energy, and for the irradiation with 15 MeV electrons as a function of annealing temperature. For the irradiation with 3.5 MeV electrons the value $\Delta E_a = 0$ is found, whereas for the electron energies of 6 to 27 MeV $\Delta E_a > 0$. This agrees with the expected threshold of about 5 MeV for cluster formation by electrons. The $\Delta E_a$ values determined as a function of annealing temperature show that the annealing rate is different for different defects. A naive diffusion model is used to estimate the temperature dependencies of the diffusion of the defects in the clusters.

[54]  arXiv:1803.06954 [pdf]
Title: Spectral analyses of trans- and cis-DOCO transients via comb spectroscopy
Comments: 4 figures, 3 tables
Subjects: Chemical Physics (physics.chem-ph); Optics (physics.optics)

We use time-resolved direct frequency comb spectroscopy in the mid-infrared to obtain high-resolution rovibrational spectra of products produced from the OD+CO reaction. In this work, we present spectral analyses for isotopologues of the transient DOCO radicals from this reaction in the OD stretch region. The analyses were performed with aid of two different theoretical approaches based on both perturbation theory and variational calculations used for prediction of rovibrational spectra of polyatomic molecules. We discuss the advantages and challenges of our current approach for studying spectroscopy and dynamics of transient molecules.

[55]  arXiv:1803.06963 [pdf, other]
Title: Interpreting Theories without a Spacetime
Comments: 41 pages, 1 figure, forthcoming in the European Journal for Philosophy of Science
Subjects: History and Philosophy of Physics (physics.hist-ph); High Energy Physics - Theory (hep-th)

In this paper we have two aims: first, to draw attention to the close connexion between interpretation and scientific understanding; second, to give a detailed account of how theories without a spacetime can be interpreted, and so of how they can be understood.
In order to do so, we of course need an account of what is meant by a theory `without a spacetime': which we also provide in this paper.
We describe three tools, used by physicists, aimed at constructing interpretations which are adequate for the goal of understanding. We analyse examples from high-energy physics illustrating how physicists use these tools to construct interpretations and thereby attain understanding. The examples are: the 't Hooft approximation of gauge theories, random matrix models, causal sets, loop quantum gravity, and group field theory.

[56]  arXiv:1803.06972 [pdf]
Title: Taxonomy and Jargon in SETI as an Interdisciplinary Field of Study
Authors: Jason T. Wright
Comments: 3pp, 1 figure, presented as a white paper to the SETI Decoding Alien Intelligence Workshop held at the SETI Institute in Mountain View, CA from 14-16 March 2018. Presented at the workshop by Sofia Sheikh. Workshop white papers available at this https URL
Subjects: Popular Physics (physics.pop-ph)

While SETI is often thought of as a part of radio astronomy with optical SETI, artifact SETI, METI, and other approaches to finding intelligent life considered to be allied fields, SETI is better understood as an interdisciplinary field with many subfields, approaches, and components. In particular, Robert Bradbury has argued for a broad view of SETI between two extremes: "orthodox SETI," or radio communication SETI, and a "Dysonian Approach" that searches for the extreme effects of alien life on its environment. Here, I build on these ideas and attempt to organize the terminology and efforts of SETI within a single framework for SETI as an interdisciplinary and multipronged approach.

[57]  arXiv:1803.06976 [pdf, other]
Title: Slope limiting the velocity field in a discontinuous Galerkin divergence free two-phase flow solver
Subjects: Fluid Dynamics (physics.flu-dyn); Computational Physics (physics.comp-ph)

Solving the Navier-Stokes equations when the density field contains a large sharp discontinuity---such as a water/air free surface---is numerically challenging. Convective instabilities cause Gibbs oscillations which quickly destroy the solution. We investigate the use of slope limiters for the velocity field to overcome this problem in a way that does not compromise on the mass conservation properties. The equations are discretised using the interior penalty discontinuous Galerkin finite element method that is divergence free to machine precision.
A slope limiter made specifically for exactly divergence free (solenoidal) fields is presented and used to illustrated the difficulties in obtaining convectively stable fields that are also exactly solenoidal. The lessons learned from this are applied in constructing a simpler method based on the use of an existing scalar slope limiter applied to each velocity component.
We show by numerical examples how both presented slope limiting methods are vastly superior to the naive non-limited method. The methods can solve difficult two-phase problems with high density ratios and high Reynolds numbers---typical for marine and offshore water/air simulations---in a way that conserves mass and stops unbounded energy growth caused by the Gibbs phenomenon.

[58]  arXiv:1803.06999 [pdf, other]
Title: Pulse Shapes in High Purity Germanium Point Contact Detectors with Low Net Impurity Concentration
Subjects: Instrumentation and Detectors (physics.ins-det)

High Purity germanium point-contact detectors have low energy thresholds and excellent energy resolution over a wide energy range, and are thus widely used in nuclear and particle physics. In rare event searches, such as neutrinoless double beta decay, the point-contact geometry is of particular importance since it allows for pulse-shape discrimination, and therefore for a significant background reduction. In this paper we investigate the pulse-shape discrimination performance of ultra-high purity germanium point contact detectors. It is demonstrated that a minimal net impurity concentration is required to meet the pulse-shape performance requirements

[59]  arXiv:1803.07000 [pdf, other]
Title: Generalized Rich-Club Ordering in Networks
Authors: Matteo Cinelli
Comments: 10 pages, 5 figures
Subjects: Physics and Society (physics.soc-ph); Social and Information Networks (cs.SI)

Rich-club ordering refers to tendency of nodes with a high degree to be more interconnected than expected. In this paper we consider the concept of rich-club ordering when generalized to structural measures different from the node degree and to non-structural measures (i.e. to node metadata). The differences in considering rich-club ordering (RCO) with respect to both structural and non-structural measures is then discussed in terms of employed coefficients and of appropriate null models (link rewiring vs metadata reshuffling). Once defined a framework for the evaluation of generalized rich-club ordering (GRCO), we investigate such a phenomenon in real networks provided with node metadata. By considering different notions of node richness we compare structural and non-structural rich-club ordering, observing how external information about the network nodes is able to validate the presence of elites in networked systems.

[60]  arXiv:1803.07028 [pdf, ps, other]
Title: Speckle characterization in a cinematography projection configuration
Subjects: Applied Physics (physics.app-ph)

Due to high exploitation costs and other environmental issues, it would be desirable to phase out large cinema projection systems based on standard xenon lamps in favor of laser based projection devices. Lasers provide longer lifetime and wider color gamut of light output. But the high degree of coherence of these sources also lead to the formation of granular structures, usually known as speckle. When an imaging system is involved, as in the cinema projection case because of the capacity of the human eye to form an image of the screen, we speak about subjective speckle. In order to remove this spatial random pattern, different methods have been studied as temporal and/or spatial coherence reduction. But most of them can't be used in the context of cinema projection because they don't respect the cinematography projection standard. In our work, we have studied the possibility to reduce the subjective speckle either by changing the coherence of the light source or by studying the influence of the different elements constituting the projection display in the conditions imposed by cinematography industry. Thanks to a lasers array formed by N independant semiconductor lasers, we have measured the evolution of the subjective speckle contrast in function of the number of sources. The resulting contrast discreases as a square root function and reach a saturation level when a light pipe is used. This behavior is directly due to the light pipe which limit at its output the spatial coherence of the source. Futhermore, in a different configuration, we have studied the influence of diffusers and the magnification of the projector zoom. It has been demonstrated that magnification plays an important role on the speckle formation because it increases the coherence length determined by the light pipe. On the contrary, the diffusers placed before the light pipe doesn't change the subjective speckle.

[61]  arXiv:1803.07030 [pdf, other]
Title: Vegas: Software package for the atomistic simulation of magnetic materials
Subjects: Computational Physics (physics.comp-ph)

We present an open-source software package, Vegas, for the atomistic simulation of magnetic materials. Using the classical Heisenberg model and the Monte Carlo Metropolis algorithm, Vegas provides the required tools to simulate and analyze magnetic phenomena of a great variety of systems. Vegas stores the history of the simulation, i.e. the magnetization and energy of the system at every time step, allowing to analyze static and dynamic magnetic phenomena from results obtained in a single simulation. Also, standardized input and output file formats are employed to facilitate the simulation process and the exchange and archiving of data. We include results from simulations performed using Vegas, showing its applicability to study different magnetic phenomena.

[62]  arXiv:1803.07056 [pdf]
Title: Non-evaporable getter coating chambers for extreme high vacuum
Subjects: Accelerator Physics (physics.acc-ph)

Techniques for NEG coating a large diameter chamber are presented along with vacuum measurements in the chamber using several pumping configurations, with base pressure as low as 1.56x10^-12 Torr (N2 equivalent) with only a NEG coating and small ion pump. We then describe modifications to the NEG coating process to coat complex geometry chambers for ultra-cold atom trap experiments. Surface analysis of NEG coated samples are used to measure composition and morphology of the thin films. Finally, pressure measurements are compared for two NEG coated polarized electron source chambers: the 130 kV polarized electron source at Jefferson Lab and the upgraded 350 kV polarized 2 electron source, both of which are approaching or within the extreme high vacuum (XHV) range, defined as P<7.5x10^-13 Torr.

[63]  arXiv:1803.07063 [pdf, other]
Title: Quantized Dehydration and the Determinants of Selectivity in the NaChBac Bacterial Sodium Channel
Comments: 13 pages 7 figure + Supplemental Information
Subjects: Biological Physics (physics.bio-ph); Biomolecules (q-bio.BM)

A discrete electrostatic/diffusion model has been developed to describe the selective permeation of ion channels, based on ionic Coulomb blockade (ICB) and quantised dehydration (QD). It has been applied to describe selectivity phenomena measured in the bacterial NaChBac sodium channel and some of its mutants. Site-directed mutagenesis and the whole-cell patch-clamp technique were used to investigate how the value $Q_f$ of the fixed charge at the selectivity filter (SF) affected both valence and alike-charge selectivity. The new ICB/QD model predicts that increasing ${Q_f}$ should lead to a shift of selectivity sequences towards larger ion sizes and charges, a result that agrees with the present experiments and with earlier work. Comparison of the model with experimental data provides evidence for an {\it effective charge} $Q_f^*$ at the SF that is smaller in magnitude than the nominal $Q_f$ corresponding to the charge on the isolated protein residues. Furthermore, $Q_f^*$ was different for aspartate and glutamate charged rings and also depended on their position within the SF. It is suggested that protonation of the residues within the restricted space is an important factor in significantly reducing the effective charge of the EEEE ring. Values of $Q_f^*$ derived from experiments on the anomalous mole fraction effect (AMFE) agree well with expectations based on the ICB/QD model and have led to the first clear demonstration of the expected ICB oscillations in Ca$^{2+}$ conduction as a function of the fixed charge. Pilot studies of the dependence of Ca$^{2+}$ conduction on pH are consistent with the predictions of the model.

[64]  arXiv:1803.07065 [pdf]
Title: Sensorless Resonance Tracking of Resonant Electromagnetic Actuator through Back-EMF Estimation for Mobile Devices
Authors: Youngjun Cho
Subjects: Applied Physics (physics.app-ph); Systems and Control (cs.SY); Signal Processing (eess.SP); Dynamical Systems (math.DS)

Resonant electromagnetic actuators have been broadly used as vibration motors for mobile devices given their ability of generating relatively fast, strong, and controllable vibration force at a given resonant frequency. Mechanism of the actuators that is based on mechanical resonance, however, limits their use to a situation where their resonant frequencies are known and unshifted. In reality, there are many factors that alter the resonant frequency: for example, manufacturing tolerances, worn mechanical components such as a spring, nonlinearity in association with different input voltage levels. Here, we describe a sensorless resonance tracking method that actuates the motor and automatically detects its unknown damped natural frequency through the estimation of back electromotive force (EMF) and inner mass movements. We demonstrate the tracking performance of the proposed method through a series of experiments. This approach has the potential to control residual vibrations and then improve vibrotactile feedback, which can potentially be used for human-computer interaction, cognitive and affective neuroscience research.

Cross-lists for Tue, 20 Mar 18

[65]  arXiv:1803.06338 (cross-list from cond-mat.quant-gas) [pdf, other]
Title: Elliptic flow in a strongly-interacting normal Bose gas
Comments: 4 pages, 3 figures
Subjects: Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Atomic Physics (physics.atom-ph); Plasma Physics (physics.plasm-ph); Quantum Physics (quant-ph)

We study the anisotropic, elliptic expansion of a thermal atomic Bose gas released from an anisotropic trapping potential, for a wide range of interaction strengths across a Feshbach resonance. We show that in our system this hydrodynamic phenomenon is for all interaction strengths fully described by a microscopic kinetic model with no free parameters. The success of this description crucially relies on taking into account the reduced thermalising power of elastic collisions in a strongly interacting gas, for which we derive an analytical theory. We also perform time-resolved measurements that directly reveal the dynamics of the energy transfer between the different expansion axes.

[66]  arXiv:1803.06410 (cross-list from q-bio.QM) [pdf, other]
Title: Accurate evaluation of size and refractive index for spherical objects in quantitative phase imaging
Comments: 14 pages, 10 figures, 1 table
Subjects: Quantitative Methods (q-bio.QM); Biological Physics (physics.bio-ph)

Measuring the average refractive index (RI) of spherical objects, such as suspended cells, in quantitative phase imaging (QPI) requires a decoupling of RI and size from the QPI data. This has been commonly achieved by determining the object's radius with geometrical approaches, neglecting light-scattering. Here, we present a novel QPI fitting algorithm that reliably uncouples the RI using Mie theory and a semi-analytical, corrected Rytov approach. We assess the range of validity of this algorithm in silico and experimentally investigate various objects (oil and protein droplets, microgel beads, cells) and noise conditions. In addition, we provide important practical cues for future studies in cell biology.

[67]  arXiv:1803.06425 (cross-list from cond-mat.soft) [pdf, other]
Title: Reinforcement Learning of Artificial Microswimmers
Subjects: Soft Condensed Matter (cond-mat.soft); Biological Physics (physics.bio-ph)

The behavior of living systems is based on the experience they gained through their interactions with the environment [1]. This experience is stored in the complex biochemical networks of cells and organisms to provide a relationship between a sensed situation and what to do in this situation [2-4]. An implementation of such processes in artificial systems has been achieved through different machine learning algorithms [5, 6]. However, for microscopic systems such as artificial microswimmers which mimic propulsion as one of the basic functionalities of living systems [7, 8] such adaptive behavior and learning processes have not been implemented so far. Here we introduce machine learning algorithms to the motion of artificial microswimmers with a hybrid approach. We employ self-thermophoretic artificial microswimmers in a real world environment [9, 10] which are controlled by a real-time microscopy system to introduce reinforcement learning [11-13]. We demonstrate the solution of a standard problem of reinforcement learning - the navigation in a grid world. Due to the size of the microswimmer, noise introduced by Brownian motion if found to contribute considerably to both the learning process and the actions within a learned behavior. We extend the learning process to multiple swimmers and sharing of information. Our work represents a first step towards the integration of learning strategies into microsystems and provides a platform for the study of the emergence of adaptive and collective behavior.

[68]  arXiv:1803.06433 (cross-list from cond-mat.mtrl-sci) [pdf]
Title: Thermal conduction of one-dimensional carbon nanomaterials and nanoarchitectures
Comments: 10 pages, 10 figures
Journal-ref: Chin. Phys. B, 2018, 27 (3): 038103
Subjects: Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)

This review summarizes the current studies of the thermal transport properties of one-dimensional (1D) carbon nanomaterials and nanoarchitectures. Considering different hybridization states of carbon, emphases are laid on a variety of 1D carbon nanomaterials, such as diamond nanothreads, penta-graphene nanotubes, supernanotubes, and carbyne. Based on experimental measurements and simulation/calculation results, we discuss the dependence of the thermal conductivity of these 1D carbon nanomaterials on a wide range of factors, including the size effect, temperature influence, strain effect, and others. This review provides an overall understanding of the thermal transport properties of 1D carbon nanomaterials and nanoarchitectures, which paves the way for effective thermal management at nanoscale.

[69]  arXiv:1803.06435 (cross-list from cond-mat.mtrl-sci) [pdf]
Title: Chapter 7 - Thermal Conductivity of Diamond Nanothread
Comments: 19 pages, 13 figures
Journal-ref: A volume in Micro and Nano Technologies, 2017, Pages 185-204
Subjects: Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)

This chapter introduces the thermal conductivity of a novel one-dimensional carbon nanostructure - diamond nanothread. It starts by introducing the family of the diamond nanothread as acquired from density functional theory calculations and also its successful experimental synthesisation. It then briefs the mechanical properties of the diamond nanothreads as a fundamental for their engineering applications. After that, it focuses on the thermal transport properties of the diamond nanothreads by examining the influences from various parameters such as size, geometry, and temperature. Then, the application of diamond nanothread as reinforcements for nanocomposites is discussed. By the end of the chapter, future directions and their potential applications are discussed.

[70]  arXiv:1803.06437 (cross-list from cond-mat.mtrl-sci) [pdf]
Title: Graphene and Carbon Nanotube Hybrid Structure: A Review
Comments: 8 pages, 7 figures
Journal-ref: Procedia IUTAM,Volume 21, 2017, Pages 94-101
Subjects: Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)

Graphene has been reported with record-breaking properties which have opened up huge potential applications. Considerable amount of researches have been devoted to manipulating or modify the properties of graphene to target a more smart nanoscale device. Graphene and carbon nanotube hybrid structure (GNHS) is one of the promising graphene derivate. The synthesis process and the mechanical properties are essential for the GNHS based devices. Therefore, this review will summarise the recent progress of the highly ordered GNHS synthesis/assembly, and discuss the mechanical properties of GNHS under various conditions as obtained from molecular dynamics simulations.

[71]  arXiv:1803.06440 (cross-list from cond-mat.mtrl-sci) [pdf]
Title: Failure mechanism of monolayer graphene under hypervelocity impact of spherical projectile
Comments: 10 pages, 9 figures
Journal-ref: Scientific Reports volume 6, Article number: 33139 (2016)
Subjects: Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)

The excellent mechanical properties of graphene have enabled it as appealing candidate in the field of impact protection or protective shield. By considering a monolayer graphene membrane, in this work, we assessed its deformation mechanisms under hypervelocity impact (from 2 to 6 km/s), based on a serial of in silico studies. It is found that the cracks are formed preferentially in the zigzag directions which are consistent with that observed from tensile deformation. Specifically, the boundary condition is found to exert an obvious influence on the stress distribution and transmission during the impact process, which eventually influences the penetration energy and crack growth. For similar sample size, the circular shape graphene possesses the best impact resistance, followed by hexagonal graphene membrane. Moreover, it is found the failure shape of graphene membrane has a strong relationship with the initial kinetic energy of the projectile. The higher kinetic energy, the more number the cracks. This study provides a fundamental understanding of the deformation mechanisms of monolayer graphene under impact, which is crucial in order to facilitate their emerging future applications for impact protection, such as protective shield from orbital debris for spacecraft.

[72]  arXiv:1803.06441 (cross-list from eess.SP) [pdf, ps, other]
Title: A Novel Blaschke Unwinding Adaptive Fourier Decomposition based Signal Compression Algorithm with Application on ECG Signals
Subjects: Signal Processing (eess.SP); Data Analysis, Statistics and Probability (physics.data-an); Machine Learning (stat.ML)

This paper presents a novel signal compression algorithm based on the Blaschke unwinding adaptive Fourier decomposition (AFD). The Blaschke unwinding AFD is a newly developed signal decomposition theory. It utilizes the Nevanlinna factorization and the maximal selection principle in each decomposition step, and achieves a faster convergence rate with higher fidelity. The proposed compression algorithm is applied to the electrocardiogram signal. To assess the performance of the proposed compression algorithm, in addition to the generic assessment criteria, we consider the less discussed criteria related to the clinical needs -- for the heart rate variability analysis purpose, how accurate the R peak information is preserved is evaluated. The experiments are conducted on the MIT-BIH arrhythmia benchmark database. The results show that the proposed algorithm performs better than other state-of-the-art approaches. Meanwhile, it also well preserves the R peak information.

[73]  arXiv:1803.06473 (cross-list from astro-ph.IM) [pdf, other]
Title: Variational Inference as an alternative to MCMC for parameter estimation and model selection
Comments: 12 pages, 3 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Data Analysis, Statistics and Probability (physics.data-an)

Many problems in Astrophysics involve using Bayesian Inference to deal with problems of parameter estimation and model selection. In this paper, we introduce Variational Inference to solve these problems and compare how the results hold up to Markov Chain Monte Carlo which is the most common method. Variational Inference converts the inference problem into an optimization problem by approximating the posterior from a known family of distributions and using Kullback-Leibler divergence to measure closeness. Variational Inference takes advantage of fast optimization techniques which make it ideal to deal with large datasets and also makes it trivial to parallelize. As a proof of principle, we apply Variational Inference for parameter estimation and model comparison to four different problems in astrophysics where MCMC techniques were previously used: measuring exoplanet orbital parameters from radial velocity data, tests of periodicities in measurements of $G$, significance of a turnover in the spectral lag data of GRB 160625B , and estimating the mass of a galaxy cluster using weak lensing. We find that Variational Inference is much faster than MCMC for these problems.

[74]  arXiv:1803.06475 (cross-list from cond-mat.quant-gas) [pdf, other]
Title: Magneto-optical trapping of optically pumped metastable europium
Comments: 5 pages, 5 figures
Subjects: Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph)

The laser cooling and trapping of europium is demonstrated herein. The atoms are optically pumped to a metastable state and then loaded from an atomic-beam source via conventional Zeeman slowing and magneto-optical trapping techniques using a J=13/2 <--> J=15/2 quasi-cyclic transition. The trapped populations contained up to 1x10^7 atoms, and the density-dependent loss rate is estimated as 1x10^-10 cm^3/s from the non-exponential loss of atoms at high densities. We also observed leakage out of the quasi-cyclic transition to the J=9/2 and 11/2 metastable states, which is adequate to pump the laser-cooled atoms back to the ground state.

[75]  arXiv:1803.06515 (cross-list from quant-ph) [pdf, ps, other]
Title: From nonholonomic quantum constraint to canonical variables of photons I: true intrinsic degree of freedom
Comments: 18 pages, 1 figure
Subjects: Quantum Physics (quant-ph); Representation Theory (math.RT); Optics (physics.optics)

We report that the true intrinsic degree of freedom of the photon is neither the polarization nor the spin. It describes a local property in momentum space and is represented in the local representation by the Pauli matrices. This result is achieved by treating the transversality condition on the vector wavefunction as a nonholonomic quantum constraint. We find that the quantum constraint makes it possible to generalize the Stokes parameters to characterize the polarization of a general state. Unexpectedly, the generalized Stokes parameters are specified in a momentum-space local reference system that is fixed by another degree of freedom, called Stratton vector. Only constant Stokes parameters in one particular local reference system can convey the intrinsic degree of freedom of the photon. We show that the optical rotation is one of such processes that change the Stratton vector with the intrinsic quantum number remaining fixed. Changing the Stratton vector of the eigenstate of the helicity will give rise to a Berry's phase.

[76]  arXiv:1803.06544 (cross-list from cond-mat.soft) [pdf, ps, other]
Title: Long ligands reinforce biological adhesion under shear flow
Subjects: Soft Condensed Matter (cond-mat.soft); Biological Physics (physics.bio-ph); Cell Behavior (q-bio.CB)

In the present work the computer modelling was used to show that longer ligands allow biological cells (e.g. blood platelets) to withstand stronger flows after their adhesion to solid walls. Mechanistic model of polymer-mediated ligand-receptor adhesion between a microparticle (cell) and a flat wall was developed. Theoretical threshold between adherent and non-adherent regimes was derived analytically and approved by the simulations. These results lead to deeper understanding of numerous biophysical processes, e.g. arterial thrombosis, and to the design of new biomimetic colloid-polymer systems.

[77]  arXiv:1803.06628 (cross-list from astro-ph.IM) [pdf, ps, other]
Title: A machine learning method to separate cosmic ray electrons from protons from 10 to 100 GeV using DAMPE data
Comments: 11 pages, 8 figures, accepted for publication in RAA
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Instrumentation and Detectors (physics.ins-det)

DArk Matter Particle Explorer (DAMPE) is a general purpose high energy cosmic ray and gamma ray observatory, aiming to detect high energy electrons and gammas in the energy range 5 GeV to 10 TeV and hundreds of TeV for nuclei. This paper provides a method using machine learning to identify electrons and separate them from gammas,protons,helium and heavy nuclei with the DAMPE data from 2016 January 1 to 2017 June 30, in energy range from 10 to 100 GeV.

[78]  arXiv:1803.06722 (cross-list from quant-ph) [pdf, ps, other]
Title: Excluding joint probabilities from quantum theory
Comments: 5 pages, no figures, Rapid Communication
Journal-ref: Phys. Rev. A 97, 030102(R) (2018)
Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech); Data Analysis, Statistics and Probability (physics.data-an)

Quantum theory does not provide a unique definition for the joint probability of two non-commuting observables, which is the next important question after the Born's probability for a single observable. Instead, various definitions were suggested, e.g. via quasi-probabilities or via hidden-variable theories. After reviewing open issues of the joint probability, we relate it to quantum imprecise probabilities, which are non-contextual and are consistent with all constraints expected from a quantum probability. We study two non-commuting observables in a two-dimensional Hilbert space and show that there is no precise joint probability that applies for any quantum state and is consistent with imprecise probabilities. This contrasts to theorems by Bell and Kochen-Specker that exclude joint probabilities for more than two non-commuting observables, in Hilbert space with dimension larger than two. If measurement contexts are included into the definition, joint probabilities are not anymore excluded, but they are still constrained by imprecise probabilities.

[79]  arXiv:1803.06767 (cross-list from quant-ph) [pdf, other]
Title: Generation and detection of non-Gaussian phonon-added coherent states in optomechanical systems
Comments: 5+4 pages, 3+1 figures
Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics)

Adding excitations on a coherent state provides an effective way to observe nonclassical properties of radiation fields. Here we describe and analyse how to apply this concept to the motional state of a mechanical oscillator and present a full scheme to prepare non-Gaussian {\it phonon}-added coherent states of the mechanical motion in cavity optomechanics. We first generate a mechanical coherent state using electromagnetically induced transparency. We then add a single phonon onto the coherent state via optomechanical parametric down-conversion combined with single photon detection. We validate this single-phonon-added coherent state by using a red-detuned beam and reading out the state of the optical output field. This approach allows us to verify nonclassical properties of the phonon state, such as sub-Poissonian character and quadrature squeezing. We further show that our scheme can be directly implemented using existing devices, and is generic in nature and hence applicable to a variety of systems in opto- and electromechanics.

[80]  arXiv:1803.06809 (cross-list from quant-ph) [pdf, ps, other]
Title: Absorption interferometer based on phase modulation
Authors: Miaodi Guo, Xuemei Su
Comments: 6 pages, 5 figures
Subjects: Quantum Physics (quant-ph); Optics (physics.optics)

We propose a scheme in which an arbitrary incidence can be made perfectly reflected/transmitted if a phase setup is adjusted under a specific condition. We analyze the intracavity field variation as well as the output field with changing closed-loop phase of atomic system and relative phase of input probe beams. And we obtain the condition for perfect transmitter or reflector. By adjusting two phase setups, the medium absorption and light interference can be controlled so that photon escape from cavity can be modulated, thus the intensity switching based on phase control can be realized. Then based on the transmission/reflection analysis, total absorption of this system can be investigated. Therefore our scheme can be used as an absorption interferometer to explore the optical absorption in some complicated system. The phase delay dependent on phi_1 or phi_2 in output light intensity can be applied in the realization of quantum phase gate and subtle wave filter. And based on this scheme, we implement the state transfer between perfect transmitter/reflector and non-perfect coherent photon absorber via relative-phase modulation.

[81]  arXiv:1803.06824 (cross-list from quant-ph) [pdf, ps, other]
Title: Indeterminism in Physics, Classical Chaos and Bohmian Mechanics. Are Real Numbers Really Real?
Authors: Nicolas Gisin
Comments: 7 pages. Presented at the David Bohm Centennial Symposium, London, Octobre 2017
Subjects: Quantum Physics (quant-ph); History and Philosophy of Physics (physics.hist-ph)

It is usual to identify initial conditions of classical dynamical systems with mathematical real numbers. However, almost all real numbers contain an infinite amount of information. Since a finite volume of space can't contain more than a finite amount of information, I argue that the mathematical real numbers are not physically real. Moreover, a better terminology for the so-called real numbers is "random numbers", as their series of bits are truly random. I propose an alternative classical mechanics that uses only finite-information numbers. This alternative classical mechanics is non-deterministic, despite the use of deterministic equations, in a way similar to quantum theory. Interestingly, both alternative classical mechanics and quantum theories can be supplemented by additional variables in such a way that the supplemented theory is deterministic. Most physicists straightforwardly supplement classical theory with real numbers to which they attribute physical existence, while most physicists reject Bohmian mechanics as supplemented quantum theory, arguing that Bohmian positions have no physical reality. I argue that it is more economical and natural to accept non-determinism with potentialities as a real mode of existence, both for classical and quantum physics.

[82]  arXiv:1803.06893 (cross-list from math.NA) [pdf, other]
Title: On reference solutions and the sensitivity of the 2d Kelvin-Helmholtz instability problem
Comments: 20 pages, 11 figures, 1 table
Subjects: Numerical Analysis (math.NA); Computational Physics (physics.comp-ph); Fluid Dynamics (physics.flu-dyn)

Two-dimensional Kelvin-Helmholtz instability problems are popular examples for assessing discretizations or turbulence models for incompressible flows. Unfortunately, the results in the literature differ considerably. This paper presents computational studies of a Kelvin-Helmholtz instability problem with high order divergence-free finite element methods. Reference results in several quantities of interest are obtained for three different Reynolds numbers up to the beginning of the final vortex pairing. A mesh-independent prediction of the final pairing is not achieved due to the sensitivity of the considered problem with respect to small perturbations. A theoretical explanation of this sensitivity to small perturbations is provided based on the theory of self-organization of 2d turbulence. Possible sources of perturbations that arise in almost any numerical simulation are discussed.

[83]  arXiv:1803.06894 (cross-list from nucl-ex) [pdf, ps, other]
Title: Main features of detectors and isotopes to investigate double beta decay with increased sensitivity
Authors: A.S. Barabash
Comments: 25 pages, 2 figures, 10 tables
Journal-ref: Int. J. Mod. Phys. A 33 (2018) 1843001
Subjects: Nuclear Experiment (nucl-ex); Instrumentation and Detectors (physics.ins-det)

The current situation in double beta decay experiments , the characteristics of modern detectors and the possibility of increasing the sensitivity to neutrino mass in future experiments are discussed. The issue of the production and use of enriched isotopes in double beta decay experiments is discussed in addition.

[84]  arXiv:1803.06915 (cross-list from math.CO) [pdf, other]
Title: Exploiting symmetry in network analysis
Comments: Main Text (7 pages) plus Supplementary Information (24 pages)
Subjects: Combinatorics (math.CO); Social and Information Networks (cs.SI); Data Analysis, Statistics and Probability (physics.data-an); Physics and Society (physics.soc-ph)

Virtually all network analyses involve structural measures or metrics between pairs of vertices, or of the vertices themselves. The large amount of redundancy present in real-world networks is inherited by such measures, and this has practical consequences which have not yet been explored in full generality, nor systematically exploited by network practitioners. Here we develop a complete framework to study and quantify the effect of redundancy on arbitrary network measures, and explain how to exploit redundancy in practice, achieving, for instance, remarkable lossless compression and computational reduction ratios in several real-world networks against some popular measures.

[85]  arXiv:1803.06918 (cross-list from math.DS) [pdf, other]
Title: Correcting Observation Model Error in Data Assimilation
Subjects: Dynamical Systems (math.DS); Data Analysis, Statistics and Probability (physics.data-an)

Standard methods of data assimilation assume prior knowledge of a model that describes the system dynamics and an observation function that maps the model state to a predicted output. An accurate mapping from model state to observation space is crucial in filtering schemes when adjusting the estimate of the system state during the filter's analysis step. However, in many applications the true observation function may be unknown and the available observation model may have significant errors, resulting in a suboptimal state estimate. We propose a method for observation model error correction within the filtering framework. The procedure involves an alternating minimization algorithm used to iteratively update a given observation function to increase consistency with the model and prior observations, using ideas from attractor reconstruction. The method is demonstrated on the Lorenz 1963 and Lorenz 1996 models, and on a single-column radiative transfer model with multicloud parameterization.

[86]  arXiv:1803.07004 (cross-list from nlin.CD) [pdf, other]
Title: Capturing photoelectron motion with guiding fictitious particles
Comments: Physical Review Letters, American Physical Society, In press
Subjects: Chaotic Dynamics (nlin.CD); Atomic Physics (physics.atom-ph)

Photoelectron momentum distributions (PMDs) from atoms and molecules undergo qualitative changes as laser parameters are varied. We present a model to interpret the shape of the PMDs. The electron's motion is guided by a fictitious particle in our model, clearly characterizing two distinct dynamical behaviors: direct ionization and rescattering. As laser ellipticity is varied, our model reproduces the bifurcation in the PMDs seen in experiments.

[87]  arXiv:1803.07014 (cross-list from quant-ph) [pdf, other]
Title: Two-photon interference in the telecom C-band after frequency conversion of photons from remote quantum emitters
Authors: Jonas H. Weber (1), Benjamin Kambs (2), Jan Kettler (1), Simon Kern (1), Julian Maisch (1), Hüseyin Vural (1), Michael Jetter (1), Simone L. Portalupi (1), Christoph Becher (2), Peter Michler (1) ((1) Institut für Halbleiteroptik und Funktionelle Grenzflächen, Center for Integrated Quantum Science and Technology (IQST) and SCoPE, University of Stuttgart, Allmandring 3, 70569 Stuttgart, Germany, (2) Fachrichtung Physik, Universität des Saarlandes, Campus E 2.6, 66123 Saarbrücken, Germany)
Comments: J. H. Weber and B. Kambs contributed equally to this work
Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Applied Physics (physics.app-ph); Optics (physics.optics)

Efficient fiber-based long-distance quantum communication via quantum repeaters relies on deterministic single-photon sources at telecom wavelengths, with the potential to exploit the existing world-wide infrastructures. For upscaling the experimental complexity in quantum networking, two-photon interference (TPI) of remote non-classical emitters in the low-loss telecom bands is of utmost importance. With respect to TPI of distinct emitters, several experiments have been conducted, e.g., using trapped atoms [Beugnon2006], ions [Maunz2007], NV-centers [Bernien2012, Sipahigil2012], SiV-centers [Sipahigil2014], organic molecules [Lettow2010] and semiconductor quantum dots (QDs) [Patel2010, Flagg2010, He2013b, Gold2014, Giesz2015, Thoma2017, Reindl2017, Zopf2017]; however, the spectral range was far from the highly desirable telecom C-band. Here, we report on TPI at 1550 nm between down-converted single photons from remote QDs [Michler2017Book], demonstrating quantum frequency conversion [Zaske2012, Ates2012, Kambs2016] as precise and stable mechanism to erase the frequency difference between independent emitters. On resonance, a TPI-visibility of (29+-3)% has been observed, being only limited by spectral diffusion processes of the individual QDs [Robinson2000, Kuhlmann2015]. Up to 2-km of additional fiber channel has been introduced in both or individual signal paths with no influence on TPI-visibility, proving negligible photon wave-packet distortion. The present experiment is conducted within a local fiber network covering several rooms between two floors of the building. Our studies pave the way to establish long-distance entanglement distribution between remote solid-state emitters including interfaces with various quantum hybrid systems [DeGreve2012,Maring2017,Bock2017,Maring2018].

[88]  arXiv:1803.07016 (cross-list from cs.CE) [pdf, ps, other]
Title: Solving coupled problems of lumped parameter models in a platform for severe accidents in nuclear reactors
Subjects: Computational Engineering, Finance, and Science (cs.CE); Computational Physics (physics.comp-ph)

This paper focuses on solving coupled problems of lumped parameter models. Such problems are of interest for the simulation of severe accidents in nuclear reactors~: these coarse-grained models allow for fast calculations for statistical analysis used for risk assessment and solutions of large problems when considering the whole severe accident scenario. However, this modeling approach has several numerical flaws. Besides, in this industrial context, computational efficiency is of great importance leading to various numerical constraints. The objective of this research is to analyze the applicability of explicit coupling strategies to solve such coupled problems and to design implicit coupling schemes allowing stable and accurate computations. The proposed schemes are theoretically analyzed and tested within CEA's procor platform on a problem of heat conduction solved with coupled lumped parameter models and coupled 1D models. Numerical results are discussed and allow us to emphasize the benefits of using the designed coupling schemes instead of the usual explicit coupling schemes.

[89]  arXiv:1803.07035 (cross-list from astro-ph.SR) [pdf, other]
Title: Prandtl-Number Effects in High-Rayleigh-Number Spherical Convection
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Fluid Dynamics (physics.flu-dyn)

Convection is the predominant mechanism by which energy and angular momentum are transported in the outer portion of the Sun. The resulting overturning motions are also the primary energy source for the solar magnetic field. An accurate solar dynamo model therefore requires a complete description of the convective motions, but these motions remain poorly understood. Studying stellar convection numerically remains challenging; it occurs within a parameter regime that is extreme by computational standards. The fluid properties of the convection zone are characterized in part by the Prandtl number $\mathrm{Pr}=\nu/\kappa$, where $\nu$ is the kinematic viscosity and $\kappa$ is the thermal diffusion; in stars, $\mathrm{Pr}$ is extremely low, $\mathrm{Pr}\approx 10^{-7}$. The influence of $\mathrm{Pr}$ on the convective motions at the heart of the dynamo is not well understood since most numerical studies are limited to using $\mathrm{Pr}\approx1$. We systematically vary $\mathrm{Pr}$ and the degree of thermal forcing, characterized through a Rayleigh number, to explore its influence on the convective dynamics. For sufficiently large thermal driving, the simulations reach a so-called convective free-fall state where diffusion no longer plays an important role in the interior dynamics. Simulations with a lower $\mathrm{Pr}$ generate faster convective flows and broader ranges of scales for equivalent levels of thermal forcing. Characteristics of the spectral distribution of the velocity remain largely insensitive to changes in $\mathrm{Pr}$. Importantly, we find that $\mathrm{Pr}$ plays a key role in determining when the free-fall regime is reached by controlling the thickness of the thermal boundary layer.

[90]  arXiv:1803.07047 (cross-list from cond-mat.str-el) [pdf, other]
Title: Electromagnetic response of quantum Hall systems in dimensions five and six and beyond
Comments: 18 pages, 4 figures
Subjects: Strongly Correlated Electrons (cond-mat.str-el); Applied Physics (physics.app-ph)

Quantum Hall (QH) states are arguably the most ubiquitous examples of nontrivial topological order, requiring no special symmetry and elegantly characterized by the first Chern number. Their higher dimension generalizations are particularly interesting from both mathematical and phenomenological perspectives, and have attracted recent attention due to a few high profile experimental realizations. In this work, we derive from first principles the electromagnetic response of QH systems in arbitrary number of dimensions, and elaborate on the crucial roles played by their modified phase space density of states under the simultaneous presence of magnetic field and Berry curvature. Besides providing new mathematical results relating this phase space modification to the non-commutativity of phase space, we also show how it produces a non-topological response current at leading order, in addition to the well-known topological contributions. This unconventional response appear only in five, six or more dimensions, and can be directly investigated through a few minimal models with specially chosen fluxes. These models, together with more generic 6D QH systems, can be realized in realistic 3D experimental setups like cold atom systems through possibly entangled synthetic dimensions.

Replacements for Tue, 20 Mar 18

[91]  arXiv:1604.07217 (replaced) [pdf, ps, other]
Title: Knot Physics -- Emergent Theory of Everything
Authors: Su-Peng Kou
Comments: 19 pages, 4 figures
Subjects: General Physics (physics.gen-ph)
[92]  arXiv:1607.04478 (replaced) [pdf, ps, other]
Title: Viscosity and effective temperature of an active dense system of self-propelled particles
Comments: Total 7 pages
Subjects: Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech); Biological Physics (physics.bio-ph)
[93]  arXiv:1609.04803 (replaced) [pdf, other]
Title: Hydrodynamic series and hydrodynamization of expanding plasma in kinetic theory
Comments: 6 pages, 2 figures, v2: author added, major rewrite, mysterious off real axis singularities in the Borel plane explained (!), see also arXiv:1802.08225 [nucl-th] by Heller and Svensson; v3: references added, minor improvements in the text, first 426 terms from Eq. (8) included in the submission
Subjects: Nuclear Theory (nucl-th); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th); Fluid Dynamics (physics.flu-dyn)
[94]  arXiv:1612.09282 (replaced) [pdf, other]
Title: Interface networks in models of competing alliances
Comments: 7 pages, 8 figures
Subjects: Pattern Formation and Solitons (nlin.PS); Physics and Society (physics.soc-ph)
[95]  arXiv:1703.04401 (replaced) [pdf, other]
Title: Soft inclusion in a confined fluctuating active gel
Comments: 16 pages, 9 figures
Journal-ref: Physical Review E, 97, 032602 (2018)
Subjects: Biological Physics (physics.bio-ph); Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech)
[96]  arXiv:1703.05371 (replaced) [pdf, other]
Title: Directional Sensitivity In Light-Mass Dark Matter Searches With Single-Electron Resolution Ionization Detectors
Comments: Most recent version
Subjects: Instrumentation and Detectors (physics.ins-det); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Materials Science (cond-mat.mtrl-sci); High Energy Physics - Experiment (hep-ex); Computational Physics (physics.comp-ph)
[97]  arXiv:1704.05276 (replaced) [pdf, other]
Title: Best reply structure and equilibrium convergence in generic games
Comments: Main paper + Supplemental Information
Subjects: Physics and Society (physics.soc-ph); Adaptation and Self-Organizing Systems (nlin.AO); Economics (q-fin.EC)
[98]  arXiv:1706.04629 (replaced) [pdf, other]
Title: Verification Studies for the Noh Problem using Non-ideal Equations of State and Finite Strength Shocks
Comments: 14 pages, 7 figures, 19 images
Subjects: Fluid Dynamics (physics.flu-dyn); Computational Engineering, Finance, and Science (cs.CE); Mathematical Physics (math-ph)
[99]  arXiv:1706.06263 (replaced) [pdf]
Title: Dynamical characteristics of electromagnetic field under conditions of total reflection
Comments: 19 pages, 4 figures
Journal-ref: J. Opt. 20, No 4, 045604 (2018)
Subjects: Optics (physics.optics)
[100]  arXiv:1706.06747 (replaced) [pdf, ps, other]
Title: Bounds on quantum confinement effects in metal nanoparticles
Comments: 11 pages, 6 figures
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics)
[101]  arXiv:1706.09923 (replaced) [pdf, ps, other]
Title: A study of the dense Uniform Electron Gas with high orders of Coupled Cluster
Comments: This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in "Neufeld, V.A. and Thom, A.J.W., J. Chem. Phys. 147, 194105 (2017)" and may be found at this https URL (following this https URL)
Journal-ref: J. Chem. Phys. 147, 194105 (2017)
Subjects: Chemical Physics (physics.chem-ph); Strongly Correlated Electrons (cond-mat.str-el)
[102]  arXiv:1708.00165 (replaced) [pdf, other]
Title: Ordering dynamics of self-propelled particles in an inhomogeneous medium
Subjects: Statistical Mechanics (cond-mat.stat-mech); Soft Condensed Matter (cond-mat.soft); Biological Physics (physics.bio-ph)
[103]  arXiv:1708.08568 (replaced) [pdf, other]
Title: How directional mobility affects biodiversity in rock-paper-scissors models
Comments: 6 pages, 10 figures
Subjects: Populations and Evolution (q-bio.PE); Adaptation and Self-Organizing Systems (nlin.AO); Biological Physics (physics.bio-ph)
[104]  arXiv:1709.04160 (replaced) [pdf, ps, other]
Title: Scaling Law for Three-body Collisions in Identical Fermions with $p$-wave Interactions
Comments: 5 pages, 4 figures
Subjects: Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph)
[105]  arXiv:1709.05198 (replaced) [pdf]
Title: Tunable viscosity modification with diluted particles: When particles decrease the viscosity of complex fluids
Comments: 13+7 pages, 6+7 figures
Subjects: Soft Condensed Matter (cond-mat.soft); Fluid Dynamics (physics.flu-dyn)
[106]  arXiv:1710.01954 (replaced) [pdf, ps, other]
Title: Actuated rheology of magnetic micro-swimmers suspensions : emergence of motor and brake states
Comments: 10 pages, 6 figures, accepted in PRFluids
Subjects: Biological Physics (physics.bio-ph); Soft Condensed Matter (cond-mat.soft); Fluid Dynamics (physics.flu-dyn)
[107]  arXiv:1710.03879 (replaced) [pdf, other]
Title: Improving particle beam acceleration in plasmas
Comments: Submitted for publication
Subjects: Accelerator Physics (physics.acc-ph); Plasma Physics (physics.plasm-ph)
[108]  arXiv:1710.07591 (replaced) [pdf, other]
Title: Characterization of the hyperfine interaction of the excited $^5$D$_0$ state of Eu$^{3+}$:Y$_2$SiO$_5$
Journal-ref: Phys. Rev. B 97, 094416 (2018)
Subjects: Quantum Physics (quant-ph); Atomic Physics (physics.atom-ph)
[109]  arXiv:1711.04009 (replaced) [src]
Title: Numerical investigation into the effects of non-equilibrium plasma discharge on two-stage ignition and LTC of DME/O2/Ar Mixtures
Authors: Yao Zhang
Comments: Authorship disputes, withdrawing the paper to resolve conflicts
Subjects: Plasma Physics (physics.plasm-ph)
[110]  arXiv:1711.04227 (replaced) [pdf, other]
Title: Phase-and-amplitude recovery from a single phase contrast image using partially spatially coherent X-ray radiation
Subjects: Optics (physics.optics)
[111]  arXiv:1711.05317 (replaced) [pdf, ps, other]
Title: Correlated network of networks enhances robustness against catastrophic failures
Comments: 5 figures
Subjects: Physics and Society (physics.soc-ph); Statistical Mechanics (cond-mat.stat-mech)
[112]  arXiv:1711.05450 (replaced) [pdf, ps, other]
Title: Scattering Theory and $\mathcal{P}\mathcal{T}$-Symmetry
Authors: Ali Mostafazadeh
Comments: Slightly expanded revised version, 38 pages
Subjects: Quantum Physics (quant-ph); Mathematical Physics (math-ph); Optics (physics.optics)
[113]  arXiv:1711.09504 (replaced) [pdf, other]
Title: A Typology of Social Capital and Associated Network Measures
Subjects: Physics and Society (physics.soc-ph); Social and Information Networks (cs.SI)
[114]  arXiv:1712.08275 (replaced) [pdf, ps, other]
Title: Ultracold anions for high-precision antihydrogen experiments
Comments: 5 pages, 4 figures
Subjects: Atomic Physics (physics.atom-ph); Optics (physics.optics); Quantum Physics (quant-ph)
[115]  arXiv:1801.00022 (replaced) [pdf, other]
Title: Measurement of the Boltzmann constant by Einstein. Problem of the 5-th Experimental Physics Olympiad. Sofia 9 December 2017
Comments: Corrections and solutions of the problems are added, together with the result of the absolute champion. Text in English 17 pages, text in Bulgarian 18 pages, 12 figures and 3 tables per language
Subjects: Physics Education (physics.ed-ph)
[116]  arXiv:1801.03726 (replaced) [pdf, other]
Title: Large deviation theory for diluted Wishart random matrices
Comments: 10 pages, 6 figures
Journal-ref: Phys. Rev. E 97, 032124 (2018)
Subjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech); Data Analysis, Statistics and Probability (physics.data-an)
[117]  arXiv:1801.04588 (replaced) [pdf, ps, other]
Title: Maximal heat transfer between two parallel plates
Comments: 10 pages, 6 figures
Subjects: Fluid Dynamics (physics.flu-dyn)
[118]  arXiv:1801.05750 (replaced) [pdf, other]
Title: No exceptional precision of exceptional point sensors
Authors: W. Langbein
Subjects: Applied Physics (physics.app-ph)
[119]  arXiv:1801.07337 (replaced) [pdf]
Title: Machine Learning and Finite Element Method for Physical Systems Modeling
Subjects: Computational Engineering, Finance, and Science (cs.CE); Computational Physics (physics.comp-ph)
[120]  arXiv:1801.08844 (replaced) [pdf, other]
Title: Identification of the fragment of the 1-methylpyrene cation by mid-IR spectroscopy
Comments: Chemical Physics Letters, Elsevier, In press
Subjects: Chemical Physics (physics.chem-ph)
[121]  arXiv:1801.09492 (replaced) [pdf, ps, other]
Title: Heterogeneity effects in power-grid network models
Comments: 12 pages, 10 Figures, results recalculated following K/N -&gt; K/N_i coupling renormalization
Subjects: Physics and Society (physics.soc-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech)
[122]  arXiv:1801.10150 (replaced) [pdf, other]
Title: Odd surface waves in two-dimensional incompressible fluids
Comments: 34 pages, 7 figures, revised version: added discussion on the Hamiltonian structure and conservation laws, new references added, minor typos corrected
Subjects: Fluid Dynamics (physics.flu-dyn); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[123]  arXiv:1802.02174 (replaced) [pdf, other]
Title: A fluid-kinetic framework for self-consistent runaway-electron simulations
Comments: 7 pages, 1 figure
Subjects: Plasma Physics (physics.plasm-ph)
[124]  arXiv:1802.08901 (replaced) [pdf, ps, other]
Title: A quasi-physical dynamic reduced order model for thermospheric mass density via Hermitian Space Dynamic Mode Decomposition
Subjects: Space Physics (physics.space-ph); Atmospheric and Oceanic Physics (physics.ao-ph); Data Analysis, Statistics and Probability (physics.data-an)
[125]  arXiv:1802.10584 (replaced) [pdf, other]
[126]  arXiv:1803.03259 (replaced) [pdf, other]
Title: A reciprocal formulation of non-exponential radiative transfer. 1: Sketch and motivation
Authors: Eugene d'Eon
Comments: 14 pages, fixed typos, more clarity, notation summary table, tweaked abstract and title
Subjects: Computational Physics (physics.comp-ph); Graphics (cs.GR); Nuclear Theory (nucl-th)
[127]  arXiv:1803.03447 (replaced) [pdf, other]
Title: Probability of radiation of twisted photons in the infrared domain
Comments: 26 pp., 7 figs; formulas (15)-(22) added
Subjects: Accelerator Physics (physics.acc-ph); Optics (physics.optics)
[128]  arXiv:1803.03490 (replaced) [pdf, ps, other]
Title: Computing Transition Rates for Rare Event: When Kramers Theory meets Free Energy Landscape
Authors: François Sicard
Comments: 5 pages, 1 figure, Supplemental Material (6 pages, 3 figures)
Subjects: Statistical Mechanics (cond-mat.stat-mech); Soft Condensed Matter (cond-mat.soft); Biological Physics (physics.bio-ph); Computational Physics (physics.comp-ph)
[129]  arXiv:1803.05329 (replaced) [pdf, other]
Title: Revealing neutral bremsstrahlung in two-phase argon electroluminescence
Comments: 12 pages, 20 figures. Version2: Introduction slightly improved
Subjects: Instrumentation and Detectors (physics.ins-det); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex)
[130]  arXiv:1803.05370 (replaced) [pdf, other]
Title: Catalogue of >55 MeV Wide-longitude Solar Proton Events Observed by SOHO, ACE, and the STEREOs at $\approx$1 AU during 2009-2016
Comments: This is a pre-print of an article to be published in Solar Physics. The final authenticated version will be available online at: this https URL
Subjects: Space Physics (physics.space-ph)
[131]  arXiv:1803.05561 (replaced) [pdf, other]
Title: On the exact continuous mapping of fermions
Comments: 7-page manuscript (2 figures) with 11-page supplemental material
Subjects: Chemical Physics (physics.chem-ph); Statistical Mechanics (cond-mat.stat-mech); Quantum Physics (quant-ph)
[132]  arXiv:1803.05732 (replaced) [pdf, other]
Title: Divergence free quantum field theory using a spectral calculus of Lorentz invariant measures
Authors: John Mashford
Comments: 75 pages, 3 figures. Minor modifications. (mainly typos) Version2
Subjects: General Physics (physics.gen-ph); High Energy Physics - Theory (hep-th)
[133]  arXiv:1803.05744 (replaced) [pdf, other]
Title: First search for invisible decays of ortho-positronium confined in a vacuum cavity
Comments: 11 pages, 6 figures, 6 tables
Subjects: High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)
[ total of 133 entries: 1-133 ]
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