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An explicit finite-difference scheme is presented for solving the two-dimensional Biot equations of poroelasticity across the full range of frequencies. The key difficulty is to discretize the Johnson-Koplik-Dashen (JKD) model which…

Classical Physics · Physics 2013-12-11 Emilie Blanc , Guillaume Chiavassa , Bruno Lombard

Diffusive transport is characterized by the scaling law $(length)^{2}\propto(time)$. In this letter we show that this relationship is significantly altered in curved analogue spacetimes. This circumstance provides an opportunity to tailor…

Statistical Mechanics · Physics 2012-06-21 Matteo Smerlak

We introduce a phenomenological, physically motivated, model for the effective tidal deformability of a neutron star, adding the frequency dependence (associated with the star's fundamental mode of oscillation) that comes into play during…

General Relativity and Quantum Cosmology · Physics 2021-02-09 N. Andersson , P. Pnigouras

A one dimensional fractional diffusion model with the Riemann-Liouville fractional derivative is studied. First, a second order discretization for this derivative is presented and then an unconditionally stable weighted average finite…

Numerical Analysis · Mathematics 2011-09-13 Ercília Sousa , Can Li

We consider the inverse problem of determining different type of information about a diffusion process, described by ordinary or fractional diffusion equations stated on a bounded domain, like the density of the medium or the velocity field…

Analysis of PDEs · Mathematics 2019-07-05 Yavar Kian , Zhiyuan Li , Yikan Liu , Masahiro Yamamoto

This study investigates a class of initial-boundary value problems pertaining to the time-fractional mixed sub-diffusion and diffusion-wave equation (SDDWE). To facilitate the development of a numerical method and analysis, the original…

Numerical Analysis · Mathematics 2023-07-12 Anatoly A. Alikhanov , Mohammad Shahbazi Asl , Chengming Huang

We present a novel method to improve pharmacokinetics modeling, an essential step of drug development. Conventional models frequently fail to fully represent the intricacies of drug absorption and distribution, which limits their predictive…

Quantitative Methods · Quantitative Biology 2024-12-31 Nazanin Ahmadi , Shupeng Wang , George Karniadakis

Using a numerical library for arbitrary precision arithmetic I study the irregular dependence of the diffusion coefficient on the slope of a piecewise linear map defining a dynamical system. I find that the graph of the diffusion…

Chaotic Dynamics · Physics 2007-05-23 Zbigniew Koza

We establish, in general terms, the conditions to be satisfied by a time-fractional approach formulation of the Poisson-Nernst-Planck model in order to guarantee that the total current across the sample be solenoidal, as required by the…

Chemical Physics · Physics 2022-01-04 G. Barbero , L. R. Evangelista , E. K. Lenzi

In this article we consider the approximation of a variable coefficient (two-sided) fractional diffusion equation (FDE), having unknown $u$. By introducing an intermediate unknown, $q$, the variable coefficient FDE is rewritten as a lower…

Numerical Analysis · Mathematics 2018-10-31 Xiangcheng Zheng , V. J. Ervin , Hong Wang

We analyse how simple local constraints in two dimensions lead a defect to exhibit robust, non-transient, and tunable, subdiffusion. We uncover a rich dynamical phenomenology realised in ice- and dimer-type models. On the microscopic scale…

Mesoscale and Nanoscale Physics · Physics 2025-04-02 Nilotpal Chakraborty , Markus Heyl , Roderich Moessner

We consider the nonlinear Duffing oscillator in presence of fractional damping which is characteristic in different physical situations. The system is studied with a smaller and larger damping parameter value, that we call the underdamped…

Chaotic Dynamics · Physics 2024-03-18 Mattia Coccolo , Jesús M. Seoane , Stefano Lenci , Miguel A. F. Sanjuán

Diffusion models have emerged as powerful generative frameworks by progressively adding noise to data through a forward process and then reversing this process to generate realistic samples. While these models have achieved strong…

Machine Learning · Computer Science 2025-03-04 Xingzhuo Guo , Yu Zhang , Baixu Chen , Haoran Xu , Jianmin Wang , Mingsheng Long

We study the effect of advection and small diffusion on passive tracers. The advecting velocity field is assumed to have mean zero and to possess time-periodic stream lines. Using a canonical transform to action-angle variables followed by…

Fluid Dynamics · Physics 2009-11-13 Tobias Schaefer , Andrew C. Poje , Jesenko Vukadinovic

We review the time evolution of wavepackets at the metal-insulator transition in two- and three-dimensional disordered systems. The importance of scale invariance and multifractal eigenfunction fluctuations is stressed. The implications of…

Mesoscale and Nanoscale Physics · Physics 2017-02-08 Bodo Huckestein , Rochus Klesse

It is discussed the limitations of the widely used markovian approximation applied to model the turbulent refractive index in lightwave propagation. It is well-known the index is a passive scalar field. Thus, the actual knowledge about…

Optics · Physics 2009-11-10 Dario G. Perez , Luciano Zunino , Mario Garavaglia

Fractional differential equations (FDEs) are an extension of the theory of fractional calculus. However, due to the difficulty in finding analytical solutions, there have not been extensive applications of FDEs until recent decades. With…

Numerical Analysis · Mathematics 2020-07-20 Nirupama Bhattacharya , Gabriel A. Silva

This paper investigates quenching solutions of an one-dimensional, two-sided Riemann-Liouville fractional order convection-diffusion problem. Fractional order spatial derivatives are discretized using weighted averaging approximations in…

Analysis of PDEs · Mathematics 2025-03-06 Rumin Dong , Lin Zhu , Qin Sheng , Bingxin Zhao

Quasilinear perpendicular diffusion of charged particles in fluctuating electromagnetic fields is the focus of this paper. A general transport parameter for perpendicular diffusion is presented being valid for an arbitrary turbulence…

Astrophysics · Physics 2007-05-23 O. Stawicki

The time discretization of stochastic spectral fractional wave equation is studied by using the difference methods. Firstly, we exploit rectangle formula to get a low order time discretization, whose the strong convergence order is smaller…

Numerical Analysis · Mathematics 2021-06-08 Xing Liu