arXiv subjects

H. Ouerdiane

Publications and source records attributed to H. Ouerdiane.

6 recordsLinked to original sources

arXiv2019

Stochastic stability of invariant measures: The 2D Euler equation

In finite-dimensional dynamical systems, stochastic stability provides the selection of physical relevant measures from the myriad invariant measures of conservative systems. That this might also apply to infinite-dimensional systems is the inspiration for this work. As an example the 2D Euler equation is studied. Among other results this study suggests that the coherent structures observed in 2D hydrodynamics are associated to configurations that maximize stochastically stable measures uniquely determined by the boundary conditions in mode space.

math.DS↗

arXiv2008

Stochastic solution of a nonlinear fractional differential equation

A stochastic solution is constructed for a fractional generalization of the KPP (Kolmogorov, Petrovskii, Piskunov) equation. The solution uses a fractional generalization of the branching exponential process and propagation processes which are spectral integrals of Levy processes

math.PR↗

arXiv2008

Representation of mean-periodic functions in series of exponential polynomials

Let $θ$ be a Young function and consider the space $\mathcal{F}_θ(\C)$ of all entire functions with $θ$-exponential growth. In this paper, we are interested in the solutions $f\in \mathcal{F}_θ(\C)$ of the convolution equation $T\star f=0$, called mean-periodic functions, where $T$ is in the topological dual of $\mathcal{F}_θ(\C)$. We show that each mean-periodic function can be represented in an explicit way as a convergent series of exponential polynomials.

math.CV↗

arXiv2006

Feynman graphs for non-Gaussian measures

Partition- and moment functions for a general (not necessarily Gaussian) functional measure that is perturbed by a Gibbs factor are calculated using generalized Feynman graphs. From the graphical calculus, a new notion of Wick ordering arises, that coincides with orthogonal decompositions of Wiener-Itô type only if the measure is Gaussian. Proving a generalized linked cluster theorem, we show that the logarithm of the partition function can be expanded in terms of connected Feynman graphs ("linked cluster theorem").

math-ph↗

arXiv2006

Convolution calculus on white noise spaces and Feynman graph representation of generalized renormalization flows

In this note we outline some novel connections between the following fields: 1) Convolution calculus on white noise spaces 2) Pseudo-differential operators and Lévy processes on infinite dimensional spaces 3) Feynman graph representations of convolution semigroups 4) generalized renormalization group flows and 5) the thermodynamic limit of particle systems.

math-ph↗

arXiv2004

Feynman graph representation of the perturbation series for general functional measures

A representation of the perturbation series of a general functional measure is given in terms of generalized Feynman graphs and -rules. The graphical calculus is applied to certain functional measures of Lévy type. A graphical notion of Wick ordering is introduced and is compared with orthogonal decompositions of the Wiener-Itô-Segal type. It is also shown that the linked cluster theorem for Feynman graphs extends to generalized Feynman graphs. We perturbatively prove existence of the thermodynamic limit for the free energy density and the moment functions. The results are applied to the gas of charged microscopic or mesoscopic particles -- neutral in average -- in $d=2$ dimensions generating a static field $ϕ$ with quadratic energy density giving rise to a pair interaction. The pressure function for this system is calculated up to fourth order. We also discuss the subtraction of logarithmically divergent self-energy terms for a gas of only one particle type by a local counterterm of first order.

math-ph↗