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Understanding the thermal equilibrium (stability) curve may offer insights into the nature of the warm absorbers often found in active galactic nuclei. Its shape is determined by factors like the spectrum of the ionizing continuum and the…

Astrophysics · Physics 2009-11-13 Susmita Chakravorty , Ajit K. Kembhavi , Martin Elvis , Gary Ferland , N. R. Badnell

The chaotic diffusion for particles moving in a time dependent potential well is described by using two different procedures: (i) via direct evolution of the mapping describing the dynamics and ; (ii) by the solution of the diffusion…

Statistical Mechanics · Physics 2020-08-26 Edson D. Leonel , Celia Mayumi Kuwana , Makoto Yoshida , Juliano Antonio de Oliveira

Space and time scales are not independent in diffusion. In fact, numerical simulations show that different patterns are obtained when space and time steps ($\Delta x$ and $\Delta t$) are varied independently. On the other hand, anisotropy…

patt-sol · Physics 2015-06-26 Rui Dilao , Joaquim Sainhas

We investigate a specific reaction-diffusion system that admits a monostable pulled front propagating at constant critical speed. When a small parameter changes sign, the stable equilibrium behind the front destabilizes, due to essential…

Analysis of PDEs · Mathematics 2021-10-07 Louis Garénaux

The effect on parametric instability growth of pump wave incoherence is treated by deriving a set of equations governing the space-time evolution of the ensemble-average coupled-mode amplitudes and intensities. Particular attention is paid…

Plasma Physics · Physics 2007-10-12 D. Pesme , R. L. Berger , E. A. Williams , A. Bourdier , A. Bortuzzo-Lesne

Thermal-diffusional pulsation behaviors in planar as well as outwardly and inwardly propagating white dwarf carbon flames are systematically studied. In the 1D numerical simulation, the asymptotic degenerate equation of state and simplified…

High Energy Astrophysical Phenomena · Physics 2017-05-31 Guangzheng Xing , Yibo Zhao , Mikhail Modestov , Cheng Zhou , Yang Gao , Chung K. Law

A variety of boundary value problems in linear transport theory are expressed as a diffusion equation of the two-way, or forward-backward, type. In such problems boundary data are specified only on part of the boundary, which introduces…

Mathematical Physics · Physics 2019-02-18 Caleb G. Wagner , Richard Beals

We address the dynamics of damped collective modes in terms of first and second moments. The modes are introduced in a self-consistent fashion with the help of a suitable application of linear response theory. Quantum effects in the…

Nuclear Theory · Physics 2015-06-26 H. Hofmann , D. Kiderlen

We consider a finite element approximation for a system consisting of the evolution of a closed planar curve by forced curve shortening flow coupled to a reaction-diffusion equation on the evolving curve. The scheme for the curve evolution…

Numerical Analysis · Mathematics 2016-07-07 John W. Barrett , Klaus Deckelnick , Vanessa Styles

Layered stable (multivariate) distributions and processes are defined and studied. A layered stable process combines stable trends of two different indices, one of them possibly Gaussian. More precisely, in short time, it is close to a…

Probability · Mathematics 2023-04-11 C. Houdré , R. Kawai

The selective frequency damping method was applied to a bent flow. The method was used in an adaptive formulation. The most dangerous frequency was determined by solving an eigenvalue problem. It was found that one of the patterns,…

Fluid Dynamics · Physics 2020-11-06 Alexander V. Proskurin

We consider some reaction-diffusion equations describing systems with the nonlocal consumption of resources and the intraspecific competition. Sharp conditions on the coefficients are obtained to ensure the stability and instability of…

Analysis of PDEs · Mathematics 2024-09-06 Yuming Chen , Vitali Vougalter

Diffusion-based posterior samplers use pretrained diffusion priors to sample from measurement- or reward-conditioned posteriors, and are widely used for inverse problems. Yet their theoretical behavior remains poorly understood: even with…

Machine Learning · Computer Science 2026-05-08 Matias G. Delgadino , Sebastien Motsch , Advait Parulekar , William Porteous , Sanjay Shakkottai

Predictive simulations of mixed plasma discharges, like deuterium-tritium plasmas, rely on self-consistent models for particle transport. These models have to be validated with interpretive analysis of existing experiments. Accounting for…

This paper is concerned with analysis of coupled fractional reaction-diffusion equations. It provides analytical comparison for the fractional and regular reaction-diffusion systems. As an example, the reaction-diffusion model with cubic…

Adaptation and Self-Organizing Systems · Physics 2007-05-23 Vasyl Gafiychuk , Bohdan Datsko , Vitaliy Meleshko

Turbulent thermal diffusion is a combined effect of the temperature stratified turbulence and inertia of small particles. It causes the appearance of a non-diffusive turbulent flux of particles in the direction of the turbulent heat flux.…

Fluid Dynamics · Physics 2018-05-24 G. Amir , N. Bar , A. Eidelman , T. Elperin , N. Kleeorin , I. Rogachevskii

Kappa-distributed velocities in plasmas are common in a wide variety of settings, from low-density to high-density plasmas. To date, they have been found mainly in space plasmas, but are recently being considered also in the modelling of…

Statistical Mechanics · Physics 2025-03-25 Sergio Davis , Gonzalo Avaria , Biswajit Bora , Jalaj Jain , José Moreno , Cristian Pavez , Leopoldo Soto

We consider transport properties of the chaotic (strange) attractor along unfolded trajectories of the dissipative standard map. It is shown that the diffusion process is normal except of the cases when a control parameter is close to some…

Chaotic Dynamics · Physics 2009-11-13 G. M. Zaslavsky , M. Edelman

Using kinetic Monte Carlo simulations and a bond-counting ansatz, thermal stability and diffusion of an adatom island on a crystal surface are studied. At low temperatures, the diffusion constant $D$ is found to decrease for a wide range of…

Condensed Matter · Physics 2009-10-31 T. Muller , W. Selke

Signaling molecules play an important role for many cellular functions. We investigate here a general system of two membrane reaction-diffusion equations coupled to a diffusion equation inside the cell by a Robin-type boundary condition and…

Analysis of PDEs · Mathematics 2015-06-16 Andreas Rätz , Matthias Röger