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We show that a unified and maximally generalized approach to spatial transformation design is possible, one that encompasses all second order waves, rays, and diffusion processes in anisotropic media. Until the final step, it is unnecessary…

Classical Physics · Physics 2018-05-04 Paul Kinsler , Martin W. McCall

The diffraction pattern of a single non-periodic compact object, such as a molecule, is continuous and is proportional to the square modulus of the Fourier transform of that object. When arrayed in a crystal, the coherent sum of the…

In this paper we explore numerically the evolution of a warped accretion disc. Here, we focus here on the regime where the warp evolves diffusively. By comparing the numerical results to a simple diffusion model, we are able to determine…

Astrophysics · Physics 2009-11-13 Giuseppe Lodato , J. E. Pringle

Diffusion in an evolving environment is studied by continuos-time Monte Carlo simulations. Diffusion is modelled by continuos-time random walkers on a lattice, in a dynamic environment provided by bubbles between two one-dimensional…

Soft Condensed Matter · Physics 2010-11-22 Janne Juntunen , Juha Merikoski

Application of fractional calculus to the description of anomalous diffusion and relaxation processes in complex media provided one of the most impressive impulses to the development of statistical physics during the last decade. In…

Soft Condensed Matter · Physics 2008-11-13 A. E. Sitnitsky

Photon transport through a diffusing slab can be described by the radiative transfer equation (RTE). When the slab is highly scattering and weakly absorbing, the RTE simplifies to the diffusion equation. In this paper, an inverse diffusion…

The position $x(t)$ of a particle diffusing in a one-dimensional uncorrelated and time dependent random medium is simply Gaussian distributed in the typical direction, i.e. along the ray $x=v_0 t$, where $v_0$ is the average drift. However,…

Statistical Mechanics · Physics 2021-08-05 Guillaume Barraquand , Pierre Le Doussal

In this work, a two-dimensional time-fractional subdiffusion model is developed to investigate the underlying transport phenomena evolving in a binary medium comprised of two sub-domains occupied by homogeneous material. We utilise an…

Numerical Analysis · Mathematics 2021-02-05 Libo Feng , Ian Turner , Patrick Perre , Kevin Burrage

The spreading of density fluctuations in two-dimensional driven diffusive systems is marginally anomalous. Mode coupling theory predicts that the diffusivity in the direction of the drive diverges with time as $(\ln t)^{2/3}$ with a…

Statistical Mechanics · Physics 2018-03-23 Joachim Krug , Robert A. Neiss , Andreas Schadschneider , Johannes Schmidt

We obtain the angular distribution of the cosmic rays reaching an observer from an individual source and after propagation through a turbulent magnetic field, for different ratios between the source distance and the diffusion length. We…

High Energy Astrophysical Phenomena · Physics 2016-03-23 Diego Harari , Silvia Mollerach , Esteban Roulet

Here we characterize the motility of athermal swimming droplets within the framework of active rotational diffusion. Just like active colloids, their trajectories can be modeled with a constant velocity $V$ and a slow angular diffusion, but…

Soft Condensed Matter · Physics 2020-05-20 Adrien Izzet , Pepijn Moerman , Jan Groenewold , Jérôme Bibette , Jasna Brujić

This paper considers the refraction and diffraction of waves in three-dimensional crystals formed by anisotropically scattering centers. The partial wave expansion method is used to consider the effect of multiple rescattering of waves by…

Optics · Physics 2013-07-08 V. G. Baryshevsky , E. A. Gurnevich

We evaluate the scattering functions of a gas of spin-polarized, non-interacting fermions confined in a quasi-onedimensional harmonic trap at zero temperature. The main focus is on the inelastic scattering spectrum and on the angular…

Statistical Mechanics · Physics 2009-11-07 Patrizia Vignolo , Anna Minguzzi , M. P. Tosi

Anomalous diffusion phenomena are ubiquitous in complex media, such as biological tissues. A wide class of sub-diffusive phenomena phenomena is described by the time-fractional diffusion equation. The paper investigates the case of…

Classical Analysis and ODEs · Mathematics 2018-10-02 Dimiter Prodanov

Thanks to their unique properties, nematic liquid crystals feature a variety of mechanisms for light-matter interactions. For continuous-wave optical excitations, the two dominant contributions stem from reorientational and thermal…

The subject matter of this paper concerns anisotropic diffusion equations: we consider heat equations whose diffusion matrix have disparate eigenvalues. We determine first and second order approximations, we study the well-posedness of them…

Analysis of PDEs · Mathematics 2012-10-24 Mihai Bostan

Light propagation in turbulent media is conventionally studied with the help of the spatio-temporal power spectra of the refractive index fluctuations. In particular, for natural water turbulence several models for the spatial power spectra…

Atmospheric and Oceanic Physics · Physics 2021-01-28 Jinren Yao , Hantao Wang , Huajun Zhang , Jiandong Cai , Mingyuan Ren , Yu Zhang , Olga Korotkova

We study the 2D motion of colloidal dimers by single-particle tracking and compare the experimental observations obtained by bright-field microscopy to theoretical predictions for anisotropic diffusion. The comparison is based on the…

We discuss a new phenomenon of turbulent thermal diffusion associated with turbulent transport of aerosols in the atmosphere and in laboratory experiments. The essence of this phenomenon is the appearance of a nondiffusive mean flux of…

Astrophysics · Physics 2020-01-29 A. Eidelman , T. Elperin , N. Kleeorin , A. Krein , I. Rogachevskii , J. Buchholz , G. Gruenefeld

Liquid crystals (LCs) play a fundamental and significant role in modern technology. Recently, they have also been used in active switching, adaptive optics, and next-generation displays for augmented and virtual reality. This is due to the…

Optics · Physics 2022-08-18 N. Madadi , M. Amiri