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We present some analytical solutions to the Einstein equations, describing radiating collapsing spheres in the diffusion approximation. Solutions allow for modeling physical reasonable situations. The temperature is calculated for each…

General Relativity and Quantum Cosmology · Physics 2008-11-26 L. Herrera , A. Di Prisco , J. Ospino

We establish a general connection between ballistic and diffusive transport in systems where the ballistic contribution in canonical ensemble vanishes. A lower bound on the Green-Kubo diffusion constant is derived in terms of the curvature…

Statistical Mechanics · Physics 2017-08-29 Marko Medenjak , Christoph Karrasch , Tomaz Prosen

We consider the wave equation for sound in a moving fluid with a fourth-order anomalous dispersion relation. The velocity of the fluid is a linear function of position, giving two points in the flow where the fluid velocity matches the…

General Relativity and Quantum Cosmology · Physics 2016-09-29 T. G. Philbin

We provide a stochastic fractional diffusion equation description of energy transport through a finite one-dimensional chain of harmonic oscillators with stochastic momentum exchange and connected to Langevian type heat baths at the…

Statistical Mechanics · Physics 2019-05-22 Aritra Kundu , Cédric Bernardin , Keji Saito , Anupam Kundu , Abhishek Dhar

We consider the dispersion properties of tracer particles moving in non-equilibrium heterogeneous periodic media. The tracer motion is described by a Fokker-Planck equation with arbitrary spatially periodic (but constant in time) local…

Statistical Mechanics · Physics 2015-12-09 T. Guérin , D. S. Dean

Quantum simulation methods based on density-functional theory are currently deemed unfit to cope with atomic heat transport within the Green-Kubo formalism, because quantum-mechanical energy densities and currents are inherently ill-defined…

Materials Science · Physics 2016-01-20 Aris Marcolongo , Paolo Umari , Stefano Baroni

We consider singularly perturbed convection-diffusion equations on one-dimensional networks (metric graphs) as well as the transport problems arising in the vanishing diffusion limit. Suitable coupling condition at inner vertices are…

Analysis of PDEs · Mathematics 2020-04-22 Herbert Egger , Nora Philippi

The aim of this paper is to discuss the appropriate modelling of in- and outflow boundary conditions for nonlinear drift-diffusion models for the transport of particles including size exclusion and their effect on the behaviour of…

Analysis of PDEs · Mathematics 2016-11-03 Martin Burger , Jan-Frederik Pietschmann

We study the long-time dynamics of the nonlinear processes modeled by diffusion-transport partial differential equations in non-divergence form with drifts. The solutions are subject to some inhomogeneous Dirichlet boundary condition.…

Analysis of PDEs · Mathematics 2026-02-11 Luan Hoang , Akif Ibragimov

Models of astrophysical convection, such as mixing length theory, typically assume that the heat transport is independent of microphysical diffusivities. Such 'diffusion-free' behaviour is, however, not observed in numerical simulations…

Solar and Stellar Astrophysics · Physics 2025-07-10 Tom Joshi-Hartley , Matthew K. Browning , Laura K. Currie , Neil T. Lewis , Benjamin P. Brown , Simon R. W. Lance

Convection-diffusion of heat transfer is one of the important phenomena in fluid flow and industrial problems. The involved parameters, boundary conditions, and material properties are greatly affecting the same. As such, the uncertainness…

General Mathematics · Mathematics 2022-05-23 Sudipta Priyadarshini , Sukanta Nayak , Paresh Kumar Panigrahi

A heat exchanger can be modeled as a closed domain containing an incompressible fluid. The moving fluid has a temperature distribution obeying the advection-diffusion equation, with zero temperature boundary conditions at the walls.…

Fluid Dynamics · Physics 2018-02-23 Florence Marcotte , Charles R. Doering , Jean-Luc Thiffeault , William R. Young

Here, we adapt the concept of transformational thermodynamics, whereby the flux of temperature is controlled via anisotropic heterogeneous diffusivity, for the diffusion and transport of mass concentration. The n-dimensional,…

Biological Physics · Physics 2013-02-01 Sebastien Guenneau , Tania Puvirajesinghe

The flow of fluid confined between a heated rotating cylinder and a cooled stationary cylinder is a canonical experiment for the study of heat transfer in engineering. The theoretical treatment of this system is greatly simplified if the…

Fluid Dynamics · Physics 2015-09-15 Jose M. Lopez , Francisco Marques , Marc Avila

We assume that we observe $N$ independent copies of a diffusion process on a time-interval $[0,2T]$. For a given time $t$, we estimate the transition density $p_t(x,y)$, namely the conditional density of $X_{t + s}$ given $X_s = x$, under…

Statistics Theory · Mathematics 2025-05-01 Fabienne Comte , Nicolas Marie

The boundary conditions prescribing the constant traction or the so-called do-nothing conditions are frequently taken on artificial boundaries in the numerical simulations of steady flow of incompressible fluids, despite the fact that they…

Fluid Dynamics · Physics 2020-02-25 M. Lanzendörfer , J. Hron

We describe an exact and highly efficient numerical algorithm for solving a special but important class of convection-diffusion equations. These equations occur in many problems in physics, chemistry, or biology, and they are usually hard…

Computational Physics · Physics 2019-03-27 Narain Karedla , Jan Christoph Thiele , Ingo Gregor , Jörg Enderlein

In this work, we obtain the numerical temperature field to a thermally developing fluid flow inside parallel plates problem with a quantum computing method. The physical problem deals with the heat transfer of a steady state,…

Anisotropic light transport is extremely common among scattering materials, yet a comprehensive picture of how macroscopic diffusion is determined by microscopic tensor scattering coefficients is not fully established yet. In this work, we…

This paper is devoted to studying the inflow problem for an ideal polytropic model with non-viscous gas in one-dimensional half space. We showed the existence of the boundary layer in different areas. By employing the energy method, we also…

Analysis of PDEs · Mathematics 2018-06-01 Meichen Hou , Lili Fan