Fractional differential equations have attracted considerable interest because of their ability to model anomalous transport phenomena. Space fractional diffusion equations with a nonlinear reaction term have been presented and used to model many problems of practical interest. In this paper, a two-dimensional Riesz space fractional diffusion equation with a nonlinear reaction term (2D-RSFDE-NR...

n=1 An = ∅, then lim n→∞ μ(An) = 0. (1.4) Given the ring A of subsets of Ω, a function f : Ω→ R is called A-elementary, if f(Ω) is a finite subset of R and f−1({c} ∈ A for every c ∈ R such that c 6= 0. let E = EA denote the set of all A-elementary functions on E. Provided with the pointwise addition and scalar multiplication of functions, the space F of all functions f : Ω→ R is a vector space ...

We present a functional framework for the adaptive design of dictionaries where the invariance to translation, dilation, and rotation is built upfront into the primary representation space. Our key idea is to build an invariant signal representation prior to the learning stage. By doing so, we focus our effort on adapting the dictionary to the distinctive features of the signal, rather than to ...

Context and objectives In image processing, the Riesz transform was introduced as a possible extension of the Hilbert Transform in general dimension: it has many applications, like the extraction of local features in 2D signals, the demodulation of holograms, or the analysis of color images. The most easy way to implement the Riesz transform is to compute its Fourier representation by mean of 2...

It is well known that short-time expansions of heat kernels correlate to formal high-frequency expansions of spectral densities. It is also well known that the latter expansions are generally not literally true beyond the first term. However, the terms in the heat-kernel expansion correspond rigorously to quantities called Riesz means of the spectral expansion, which damp out oscillations in th...

Abstract The inequalities of Hardy-Littlewood and Riesz say that certain integrals involving products of two or three functions increase under symmetric decreasing rearrangement. It is known that these inequalities extend to integrands of the form F (u1, . . . , um) where F is supermodular; in particular, they hold when F has nonnegative mixed second derivatives ∂i∂jF for all i 6= j. This paper...