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We present a short overview of the recent results in the theory of diffusion and wave equations with generalised derivative operators. We give generic examples of such generalised diffusion and wave equations, which include time-fractional,…

Statistical Mechanics · Physics 2019-03-05 Trifce Sandev , Ralf Metzler , Aleksei Chechkin

To consider a medium carrying light and electromagnetic waves is impossible, when this medium shall have properties according to the principle of constant speed of light, that is, isotropy of speed of light in every system of reference.…

General Physics · Physics 2007-05-23 Herbert Weiss

Coherent wave control is of key importance across a broad range of fields such as electromagnetics, photonics, and acoustics. It enables us to amplify or suppress the outgoing waves via engineering amplitudes and phases of multiple…

In an anisotropic medium, the refractive index depends on the direction of propagation. Zero index in a fixed direction implies a stretching of the wave to uniformity along that axis, reducing the effective number of dimensions by one. Here…

Optics · Physics 2018-02-28 S. A. R. Horsley

Stability is a key aspect of data analysis. In many applications, the natural notion of stability is geometric, as illustrated for example in computer vision. Scattering transforms construct deep convolutional representations which are…

Machine Learning · Computer Science 2018-11-28 Fernando Gama , Alejandro Ribeiro , Joan Bruna

We generalize the invariant imbedding theory of the wave propagation and derive new invariant imbedding equations for the propagation of arbitrary number of coupled waves of any kind in arbitrarily-inhomogeneous stratified media, where the…

Optics · Physics 2009-11-10 Kihong Kim , Dong-Hun Lee , H. Lim

Deep generative models are universal tools for learning data distributions on high dimensional data spaces via a mapping to lower dimensional latent spaces. We provide a study of latent space geometries and extend and build upon previous…

Machine Learning · Computer Science 2019-02-07 Max F. Frenzel , Bogdan Teleaga , Asahi Ushio

The diffuse intensity propagating in turbid media is sensitive to the presence of any kind of object embedded in the medium, e.g. obstacles or defects. The long-ranged effects of isolated objects can be described by a stationary diffusion…

Mesoscale and Nanoscale Physics · Physics 2009-10-31 J. M. Luck , Th. M. Nieuwenhuizen

Numerical simulation of wave propagation in an infinite medium is made possible by surrounding a finite region by a perfectly matched layer (PML). Using this approach a generalized three-dimensional (3D) formulation is proposed for…

Numerical Analysis · Mathematics 2016-12-21 Hisham Assi , Richard S. C. Cobbold

Anisotropy of the permeability tensor in statistically uniform porous media of sizes used in typical computer simulations is studied. Although such systems are assumed to be isotropic by default, we show that de facto their anisotropic…

Fluid Dynamics · Physics 2015-05-13 Zbigniew Koza , Maciej Matyka , Arzhang Khalili

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

In this paper the interface between two transformation media or between a transformation medium and vacuum is studied. Strictly from the transformation optics point of view the consequences of the boundary conditions at such interfaces are…

Optics · Physics 2010-01-18 L. Bergamin

We propose a thermodynamically consistent general-purpose model describing diffusion of a solute or a fluid in a solid undergoing possible phase transformations and damage, beside possible visco-inelastic processes. Also heat…

Mathematical Physics · Physics 2015-10-28 Tomas Roubicek , Giuseppe Tomassetti

Diffusion models, which learn to reverse a signal destruction process to generate new data, typically require the signal at each step to have the same dimension. We argue that, considering the spatial redundancy in image signals, there is…

Machine Learning · Computer Science 2022-11-30 Han Zhang , Ruili Feng , Zhantao Yang , Lianghua Huang , Yu Liu , Yifei Zhang , Yujun Shen , Deli Zhao , Jingren Zhou , Fan Cheng

Diffusion models have had a profound impact on many application areas, including those where data are intrinsically infinite-dimensional, such as images or time series. The standard approach is first to discretize and then to apply…

Machine Learning · Statistics 2025-06-09 Jakiw Pidstrigach , Youssef Marzouk , Sebastian Reich , Sven Wang

One of the greatest theoretical challenges in the build-up to the era of second-generation gravitational-wave detectors is the modeling of generic binary waveforms. We introduce an approximation that has the potential to significantly…

General Relativity and Quantum Cosmology · Physics 2013-03-12 Patricia Schmidt , Mark Hannam , Sascha Husa

We propose a new model to describe diffusion processes within active deformable media. Our general theoretical framework is based on physical and mathematical considerations, and it suggests to use diffusion tensors directly coupled to…

Tissues and Organs · Quantitative Biology 2021-03-03 Christian Cherubini , Simonetta Filippi , Alessio Gizzi , Ricardo Ruiz-Baier

The propagation of a wave in a medium is generally affected when the medium is moving with respect to the observer. Because plasma equilibria often involve plasma flows, for instance in astrophysics or in magnetic confinement nuclear fusion…

Plasma Physics · Physics 2024-07-22 Aymeric Braud , Julien Langlois , Renaud Gueroult

Diffusion generative models have recently become a powerful technique for creating and modifying high-quality, coherent video content. This survey provides a comprehensive overview of the critical components of diffusion models for video…

Computer Vision and Pattern Recognition · Computer Science 2024-11-19 Andrew Melnik , Michal Ljubljanac , Cong Lu , Qi Yan , Weiming Ren , Helge Ritter

We consider the scattering of elastic waves by highly oscillating anisotropic periodic media with bounded support. Applying the two-scale homogenization, we first obtain a constant coefficient second-order partial differential elliptic…

Analysis of PDEs · Mathematics 2018-02-06 Yi-Hsuan Lin , Shixu Meng