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https://www.readbyqxmd.com/read/29906998/kappa-and-other-nonequilibrium-distributions-from-the-fokker-planck-equation-and-the-relationship-to-tsallis-entropy
#1
Bernie D Shizgal
This paper considers two nonequilibrium model systems described by linear Fokker-Planck equations for the time-dependent velocity distribution functions that yield steady state Kappa distributions for specific system parameters. The first system describes the time evolution of a charged test particle in a constant temperature heat bath of a second charged particle. The time dependence of the distribution function of the test particle is given by a Fokker-Planck equation with drift and diffusion coefficients for Coulomb collisions as well as a diffusion coefficient for wave-particle interactions...
May 2018: Physical Review. E
https://www.readbyqxmd.com/read/29906902/fokker-planck-equation-of-the-reduced-wigner-function-associated-to-an-ohmic-quantum-langevin-dynamics
#2
Pedro J Colmenares
This article has to do with the derivation and solution of the Fokker-Planck equation associated to the momentum-integrated Wigner function of a particle subjected to a harmonic external field in contact with an ohmic thermal bath of quantum harmonic oscillators. The strategy employed is a simplified version of the phenomenological approach of Schramm, Jung, and Grabert of interpreting the operators as c numbers to derive the quantum master equation arising from a twofold transformation of the Wigner function of the entire phase space...
May 2018: Physical Review. E
https://www.readbyqxmd.com/read/29906131/dark-matter-equation-of-state-through-cosmic-history
#3
Michael Kopp, Constantinos Skordis, Daniel B Thomas, Stéphane Ilić
Cold dark matter is a crucial constituent of the current concordance cosmological model. Having a vanishing equation of state (EOS), its energy density scales with the inverse cosmic volume and is thus uniquely described by a single number, its present abundance. We test the inverse cosmic volume law for dark matter (DM) by allowing its EOS to vary independently in eight redshift bins in the range z=10^{5} and z=0. We use the latest measurements of the cosmic microwave background radiation from the Planck satellite and supplement them with baryon acoustic oscillation (BAO) data from the 6dF and SDSS-III BOSS surveys and with the Hubble Space Telescope (HST) key project data...
June 1, 2018: Physical Review Letters
https://www.readbyqxmd.com/read/29864823/an-electron-beam-ion-trap-and-source-for-re-acceleration-of-rare-isotope-ion-beams-at-triumf
#4
M A Blessenohl, S Dobrodey, C Warnecke, M K Rosner, L Graham, S Paul, T M Baumann, Z Hockenbery, R Hubele, T Pfeifer, F Ames, J Dilling, J R Crespo López-Urrutia
Electron beam driven ionization can produce highly charged ions (HCIs) in a few well-defined charge states. Ideal conditions for this are maximally focused electron beams and an extremely clean vacuum environment. A cryogenic electron beam ion trap fulfills these prerequisites and delivers very pure HCI beams. The Canadian rare isotope facility with electron beam ion source-electron beam ion sources developed at the Max-Planck-Institut für Kernphysik (MPIK) reaches already for a 5 keV electron beam and a current of 1 A with a density in excess of 5000 A/cm2 by means of a 6 T axial magnetic field...
May 2018: Review of Scientific Instruments
https://www.readbyqxmd.com/read/29758691/self-avoiding-walk-on-a-square-lattice-with-correlated-vacancies
#5
J Cheraghalizadeh, M N Najafi, H Mohammadzadeh, A Saber
The self-avoiding walk on the square site-diluted correlated percolation lattice is considered. The Ising model is employed to realize the spatial correlations of the metric space. As a well-accepted result, the (generalized) Flory's mean-field relation is tested to measure the effect of correlation. After exploring a perturbative Fokker-Planck-like equation, we apply an enriched Rosenbluth Monte Carlo method to study the problem. To be more precise, the winding angle analysis is also performed from which the diffusivity parameter of Schramm-Loewner evolution theory (κ) is extracted...
April 2018: Physical Review. E
https://www.readbyqxmd.com/read/29758627/time-fractional-characterization-of-brine-reaction-and-precipitation-in-porous-media
#6
Jianping Xu, Guancheng Jiang
Brine reaction and precipitation in porous media sometimes occur in the presence of a strong fluid flowing field, which induces the mobilization of the precipitated salts and distorts their spatial distribution. It is interesting to investigate how the distribution responds to such mobilization. We view these precipitates as random walkers in the complex inner space of the porous media, where they make stochastic jumps among locations and possibly wait between successive transitions. In consideration of related experimental results, the waiting time of the precipitates at a particular position is allowed to range widely from short sojourn to permanent residence...
April 2018: Physical Review. E
https://www.readbyqxmd.com/read/29548147/semiclassical-theory-of-strong-localization-for-quantum-thermalization
#7
Christine Khripkov, Amichay Vardi, Doron Cohen
We introduce a semiclassical theory for strong localization that may arise in the context of many-body thermalization. As a minimal model for thermalization we consider a few-site Bose-Hubbard model consisting of two weakly interacting subsystems that can exchange particles. The occupation of a subsystem (x) satisfies in the classical treatment a Fokker-Planck equation with a diffusion coefficient D(x). We demonstrate that it is possible to deduce from the classical description a quantum breaktime t^{*} and, hence, the manifestations of a strong localization effect...
February 2018: Physical Review. E
https://www.readbyqxmd.com/read/29543020/probing-planckian-corrections-at-the-horizon-scale-with-lisa-binaries
#8
Andrea Maselli, Paolo Pani, Vitor Cardoso, Tiziano Abdelsalhin, Leonardo Gualtieri, Valeria Ferrari
Several quantum-gravity models of compact objects predict microscopic or even Planckian corrections at the horizon scale. We explore the possibility of measuring two model-independent, smoking-gun effects of these corrections in the gravitational waveform of a compact binary, namely, the absence of tidal heating and the presence of tidal deformability. For events detectable by the future space-based interferometer LISA, we show that the effect of tidal heating dominates and allows one to constrain putative corrections down to the Planck scale...
February 23, 2018: Physical Review Letters
https://www.readbyqxmd.com/read/29391499/chaos-and-dynamical-complexity-in-the-quantum-to-classical-transition
#9
Bibek Pokharel, Moses Z R Misplon, Walter Lynn, Peter Duggins, Kevin Hallman, Dustin Anderson, Arie Kapulkin, Arjendu K Pattanayak
We study the largest Lyapunov exponents λ and dynamical complexity for an open quantum driven double-well oscillator, mapping its dependence on coupling to the environment Γ as well as effective Planck's constant β2 . We show that in general λ increases with effective Hilbert space size (as β decreases, or the system becomes larger and closer to the classical limit). However, if the classical limit is regular, there is always a quantum system with λ greater than the classical λ, with several examples where the quantum system is chaotic even though the classical system is regular...
February 1, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29382874/phase-space-volume-scaling-of-generalized-entropies-and-anomalous-diffusion-scaling-governed-by-corresponding-non-linear-fokker-planck-equations
#10
Dániel Czégel, Sámuel G Balogh, Péter Pollner, Gergely Palla
Many physical, biological or social systems are governed by history-dependent dynamics or are composed of strongly interacting units, showing an extreme diversity of microscopic behaviour. Macroscopically, however, they can be efficiently modeled by generalizing concepts of the theory of Markovian, ergodic and weakly interacting stochastic processes. In this paper, we model stochastic processes by a family of generalized Fokker-Planck equations whose stationary solutions are equivalent to the maximum entropy distributions according to generalized entropies...
January 30, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29347760/anomalies-in-the-equilibrium-and-nonequilibrium-properties-of-correlated-ions-in-complex-molecular-environments
#11
Sathiya Mahakrishnan, Subrata Chakraborty, Amrendra Vijay
Emergent statistical attributes, and therefore the equations of state, of an assembly of interacting charge carriers embedded within a complex molecular environment frequently exhibit a variety of anomalies, particularly in the high-density (equivalently, the concentration) regime, which are not well understood, because they do not fall under the low-concentration phenomenologies of Debye-Hückel-Onsager and Poisson-Nernst-Planck, including their variants. To go beyond, we here use physical concepts and mathematical tools from quantum scattering theory, transport theory with the Stosszahlansatz of Boltzmann, and classical electrodynamics (Lorentz gauge) and obtain analytical expressions both for the average and the frequency-wave vector-dependent longitudinal and transverse current densities, diffusion coefficient, and the charge density, and therefore the analytical expressions for (a) the chemical potential, activity coefficient, and the equivalent conductivity for strong electrolytes and (b) the current-voltage characteristics for ion-transport processes in complex molecular environments...
November 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347715/cusps-enable-line-attractors-for-neural-computation
#12
Zhuocheng Xiao, Jiwei Zhang, Andrew T Sornborger, Louis Tao
Line attractors in neuronal networks have been suggested to be the basis of many brain functions, such as working memory, oculomotor control, head movement, locomotion, and sensory processing. In this paper, we make the connection between line attractors and pulse gating in feed-forward neuronal networks. In this context, because of their neutral stability along a one-dimensional manifold, line attractors are associated with a time-translational invariance that allows graded information to be propagated from one neuronal population to the next...
November 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347544/adiabatic-elimination-of-inertia-of-the-stochastic-microswimmer-driven-by-%C3%AE-stable-noise
#13
Joerg Noetel, Igor M Sokolov, Lutz Schimansky-Geier
We consider a microswimmer that moves in two dimensions at a constant speed and changes the direction of its motion due to a torque consisting of a constant and a fluctuating component. The latter will be modeled by a symmetric Lévy-stable (α-stable) noise. The purpose is to develop a kinetic approach to eliminate the angular component of the dynamics to find a coarse-grained description in the coordinate space. By defining the joint probability density function of the position and of the orientation of the particle through the Fokker-Planck equation, we derive transport equations for the position-dependent marginal density, the particle's mean velocity, and the velocity's variance...
October 2017: Physical Review. E
https://www.readbyqxmd.com/read/29341784/fractional-transport-in-strongly-turbulent-plasmas
#14
Heinz Isliker, Loukas Vlahos, Dana Constantinescu
We analyze statistically the energization of particles in a large scale environment of strong turbulence that is fragmented into a large number of distributed current filaments. The turbulent environment is generated through strongly perturbed, 3D, resistive magnetohydrodynamics simulations, and it emerges naturally from the nonlinear evolution, without a specific reconnection geometry being set up. Based on test-particle simulations, we estimate the transport coefficients in energy space for use in the classical Fokker-Planck (FP) equation, and we show that the latter fails to reproduce the simulation results...
July 28, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/29146422/numerical-study-of-the-effect-of-soft-layer-properties-on-bacterial-electroporation
#15
Jeffrey L Moran, Naga Neehar Dingari, Paulo A Garcia, Cullen R Buie
We present a numerical model of electroporation in a gram-positive bacterium, which accounts for the presence of a negatively charged soft polyelectrolyte layer (which may include a periplasmic space, peptidoglycan layer, cilia, flagella, and other surface appendages) surrounding its plasma membrane. We model the ion transport within and outside the soft layer using the soft layer electrokinetics-based Poisson-Nernst-Planck formalism. Additionally, we model the electroporation dynamics on the plasma membrane using the pore nucleation-based electroporation formalism developed by Krassowska and Filev...
September 18, 2017: Bioelectrochemistry
https://www.readbyqxmd.com/read/29101341/quantum-mechanics-as-classical-statistical-mechanics-with-an-ontic-extension-and-an-epistemic-restriction
#16
Agung Budiyono, Daniel Rohrlich
Where does quantum mechanics part ways with classical mechanics? How does quantum randomness differ fundamentally from classical randomness? We cannot fully explain how the theories differ until we can derive them within a single axiomatic framework, allowing an unambiguous account of how one theory is the limit of the other. Here we derive non-relativistic quantum mechanics and classical statistical mechanics within a common framework. The common axioms include conservation of average energy and conservation of probability current...
November 3, 2017: Nature Communications
https://www.readbyqxmd.com/read/28991743/curvature-integration-in-a-5d-kernel-for-extracting-vessel-connections-in-retinal-images
#17
Samaneh Abbasi-Sureshjani, Marta Favali, Giovanna Citti, Alessandro Sarti, Bart M Ter Haar Romeny
Tree-like structures, such as retinal images, are widely studied in computer-aided diagnosis systems for large-scale screening programs. Despite several segmentation and tracking methods proposed in the literature, there still exist several limitations specifically when two or more curvilinear structures cross or bifurcate, or in the presence of interrupted lines or highly curved blood vessels. In this paper, we propose a novel approach based on multi-orientation scores augmented with a contextual affinity matrix, which both are inspired by the geometry of the primary visual cortex (V1) and their contextual connections...
February 2018: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
https://www.readbyqxmd.com/read/28949174/no-evidence-for-extensions-to-the-standard-cosmological-model
#18
Alan Heavens, Yabebal Fantaye, Elena Sellentin, Hans Eggers, Zafiirah Hosenie, Steve Kroon, Arrykrishna Mootoovaloo
We compute the Bayesian evidence for models considered in the main analysis of Planck cosmic microwave background data. By utilizing carefully defined nearest-neighbor distances in parameter space, we reuse the Monte Carlo Markov chains already produced for parameter inference to compute Bayes factors B for many different model-data set combinations. The standard 6-parameter flat cold dark matter model with a cosmological constant (ΛCDM) is favored over all other models considered, with curvature being mildly favored only when cosmic microwave background lensing is not included...
September 8, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28891501/a-comparison-of-computational-models-for-the-extracellular-potential-of-neurons
#19
Jurgis Pods
The extracellular space has an ambiguous role in neuroscience. It is present in every physiologically relevant system and often used as a measurement site in experimental recordings, but it has received subordinate attention compared to the intracellular domain. In computational modeling, it is often regarded as a passive, homogeneous resistive medium with a constant conductivity, which greatly simplifies the computation of extracellular potentials. However, novel studies have shown that local ionic diffusion and capacitive effects of electrically active membranes can have a substantial impact on the extracellular potential...
2017: Journal of Integrative Neuroscience
https://www.readbyqxmd.com/read/28863683/portable-double-sided-pulsed-laser-heating-system-for-time-resolved-geoscience-and-materials-science-applications
#20
G Aprilis, C Strohm, I Kupenko, S Linhardt, A Laskin, D M Vasiukov, V Cerantola, E G Koemets, C McCammon, A Kurnosov, A I Chumakov, R Rüffer, N Dubrovinskaia, L Dubrovinsky
A portable double-sided pulsed laser heating system for diamond anvil cells has been developed that is able to stably produce laser pulses as short as a few microseconds with repetition frequencies up to 100 kHz. In situ temperature determination is possible by collecting and fitting the thermal radiation spectrum for a specific wavelength range (particularly, between 650 nm and 850 nm) to the Planck radiation function. Surface temperature information can also be time-resolved by using a gated detector that is synchronized with the laser pulse modulation and space-resolved with the implementation of a multi-point thermal radiation collection technique...
August 2017: Review of Scientific Instruments
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