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In this article we study the numerical approximation of a variable coefficient fractional diffusion equation. Using a change of variable, the variable coefficient fractional diffusion equation is transformed into a constant coefficient…

Numerical Analysis · Mathematics 2019-02-28 Xiangcheng Zheng , V. J. Ervin , Hong Wang

An important contribution to the gamma-ray emission of our Galaxy is the Galactic Diffuse emission. We present specific developments within the PICARD code for modeling of Galactic cosmic ray propagation that are relevant for the…

High Energy Astrophysical Phenomena · Physics 2017-01-26 Felix Niederwanger , Olaf Reimer , Ralf Kissmann , Richard Tuffs

The analysis of diffusion processes in real-world propagation scenarios often involves estimating variables that are not directly observed. These hidden variables include parental relationships, the strengths of connections between nodes,…

Social and Information Networks · Computer Science 2016-05-12 Shohreh Shaghaghian , Mark Coates

We study the weak error associated with the Euler scheme of non degenerate diffusion processes with non smooth bounded coefficients. Namely, we consider the cases of H{\"o}lder continuous coefficients as well as piecewise smooth drifts with…

Probability · Mathematics 2016-12-28 V Konakov , S Menozzi

Diffusion-based generative models in SE(3)-invariant space have demonstrated promising performance in molecular conformation generation, but typically require solving stochastic differential equations (SDEs) with thousands of update steps.…

Computational Physics · Physics 2024-02-02 Zihan Zhou , Ruiying Liu , Tianshu Yu

We introduce a general framework for solving partial differential equations (PDEs) using generative diffusion models. In particular, we focus on the scenarios where we do not have the full knowledge of the scene necessary to apply classical…

Machine Learning · Computer Science 2024-11-04 Jiahe Huang , Guandao Yang , Zichen Wang , Jeong Joon Park

In a recent Comment on our Letter (Phys. Rev. Lett, Vol 76, p 3886 (1996); astro-ph/9605001) Evans (astro-ph/9606155) has raised some issues concerning the specific choice of the distribution function used in our calculation. He has also…

Astrophysics · Physics 2007-05-23 R. Cowsik , Charu Ratnam , P. Bhattacharjee

A diffusive lattice gas is characterized by the diffusion coefficient depending only on the density. The Green-Kubo formula for diffusivity can be represented as a variational formula, but even when the equilibrium properties of a lattice…

Statistical Mechanics · Physics 2017-03-10 Chikashi Arita , P. L. Krapivsky , Kirone Mallick

Diffusion is a fundamental physical phenomenon with critical applications in fields such as metallurgy, cell biology, and population dynamics. While standard diffusion is well-understood, anomalous diffusion often requires complex non-local…

Statistical Mechanics · Physics 2026-01-16 Gabriel Barreiro , Vladimir Pérez-Veloz

These comments aim to correct some apparent weaknesses in the theory of field electron emission given in a recent paper about nanoscale vacuum channel transistors, and to improve the presentation of this theory. In particular, it is argued…

Mesoscale and Nanoscale Physics · Physics 2021-02-24 Richard G. Forbes

We expand the classic variational formulation of $-\log\mathbb{E}\left[e^{-f}\right]$ to the case where f depends on a diffusion, and not only a on Brownian motion, while decreasing the integrability hypothesis on f. We also give an…

Probability · Mathematics 2016-12-02 Kévin Hartmann

The aim of this paper is the rigorous derivation of a stochastic non-linear diffusion equation from a radiative transfer equation perturbed with a random noise. The proof of the convergence relies on a formal Hilbert expansion and the…

Analysis of PDEs · Mathematics 2014-05-13 Arnaud Debussche , Sylvain De Moor , Julien Vovelle

In this paper a concentration inequality is proved for the deviation in the ergodic theorem in the case of discrete time observations of diffusion processes. The proof is based on the geometric ergodicity property for diffusion processes.…

Probability · Mathematics 2011-09-16 Leonid Galtchouk , Serguei Pergamenchtchikov

We study nonparametric estimation of the diffusion coefficient from discrete data, when the observations are blurred by additional noise. Such issues have been developed over the last 10 years in several application fields and in particular…

Statistics Theory · Mathematics 2011-12-30 Marc Hoffmann , Axel Munk , Johannes Schmidt-Hieber

One key issue in the probability density function (PDF) approach for disperse two-phase turbulent flows is to close the diffusion term in the phase space. This study aimed to derive a kinetic equation for particle dispersion in turbulent…

Statistical Mechanics · Physics 2020-07-15 De-yu Zhong , Guang-qian Wang , Tie-jian Li , Ming-xi Zhang , You Xia

Recently, there has been interest in determining the viscoelastic properties of polymeric liquids and other complex fluids by means of Diffusing Wave Spectroscopy (DWS). In this technique, light-scattering spectroscopy is applied to highly…

Soft Condensed Matter · Physics 2024-08-27 George D. J. Phillies

Translational diffusion coefficients are routinely estimated from molecular dynamics simulations. Linear fits to mean squared displacement (MSD) curves have become the de facto standard, from simple liquids to complex biomacromolecules.…

Computational Physics · Physics 2020-11-20 Jakob Tómas Bullerjahn , Sören von Bülow , Gerhard Hummer

We develop a practical method of computing the stationary drift velocity V and the diffusion coefficient D of a particle (or a few particles) in a periodic system with arbitrary transition rates. We solve this problem both in a physically…

Statistical Mechanics · Physics 2009-10-31 Zbigniew Koza

Global Navigation Satellite Systems (GNSS) are vital for reliable urban positioning. However, multipath and non-line-of-sight reception often introduce large measurement errors that degrade accuracy. Learning-based methods for predicting…

Computer Vision and Pattern Recognition · Computer Science 2025-09-23 Jiaqi Zhu , Shouyi Lu , Ziyao Li , Guirong Zhuo , Lu Xiong

The ultra high-energy (UHE) Galactic diffuse gamma-ray emission holds important information on the propagation of cosmic rays in the Galaxy. However, its measurements suffer from a contamination from unresolved sources whose contribution…

High Energy Astrophysical Phenomena · Physics 2024-11-04 Samy Kaci , Gwenael Giacinti , Dmitri Semikoz