arXiv subjects

Christophe Cheverry

Publications and source records attributed to Christophe Cheverry.

11 recordsLinked to original sources

arXiv2026

The Schr\"odinger-Klein-Gordon System Revisited

We introduce a microlocal formulation of the Schr{\"o}dinger-Klein-Gordon system describing the interaction between a non-relativistic quantum particle and a Klein-Gordon field through Yukawa coupling. Instead of working directly with the Schr{\"o}dinger wave function, we represent the quantum component by its Fourier-Wigner transform, and we rewrite the Klein-Gordon equation in terms of a complex Fourier variable. Eliminating the field variable yields a closed nonlinear Fourier-Moyal equation on phase space whose unknown is the Fourier-Wigner distribution associated with the quantum component. The resulting formulation provides a refined description of the particle-field interaction at the microlocal level. In particular, the original cubic coupling is transformed into a quadratic self-interaction governed by an explicit bilinear operator. This new representation permits the use of techniques from time-frequency analysis. Building on this, we develop a well-posedness theory for the Fourier-Moyal equation in anisotropic spaces involving Wiener-type norms and prescribed moduli of continuity. Local existence and uniqueness are established under general assumptions on the ultraviolet cutoff, together with propagation of microlocal regularity. We then introduce a new construction of weak L 2 -solutions by exploiting compactness properties of Fourier-Wigner transforms and obtain global existence for prepared data. The aim is to provide an alternative analytical framework for the study of Yukawa-type interactions and to establish a bridge between nonlinear dispersive equations and phase-space methods.

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arXiv2026

The Fast Limit Model Associated With The Euler-Maxwell-Two-Fluid System

The filtering method applied at the level of the Euler-Maxwell-Two-Fluid system produces a Fast Limit Model (FLM) which captures up to the electron depth essential features of plasma dynamics. In the case of prepared data, the discussion reduces to the eXtended MagnetoHydroDynamic (XMHD) framework of physicists, which involves the density __, the velocity u and the magnetic field B as state variables. By contrast, for unprepared data, an electric field E is created by resonances, and it participates to the time evolution. It turns out that FLM is a well-posed system on (__, u, E, B), extending XMHD, and implying a mechanism of interactions between (__, u, B) and E which can convert a part of the energy carried by (__, u, B) into electric energy.

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arXiv2025

The incompressible limit of the Euler-Maxwell two-fluid system

In this text, the filtering unitary group method developed, among others, by S. Schochet is adapted to prove the existence and well-posedness of modulation equations describing the incompressible limit of the Euler-Maxwell Two-Fluid (EMTF) system. The reduced model captures up to the ion and electron skin depths the long-time behavior of solutions near a constant neutral background with non-zero densities. In the prepared case, the solutions of our asymptotic equations are in one-to-one correspondence with those of incompressible eXtended MagnetoHyDrodynamics (XMHD), hence providing a new basis to the XMHD framework which is currently being studied by physicists through Hamiltonian methods, see P.J. Morrison et al. By this way, we can give a simplified access to many plasma phenomena such as (a form of two-fluid) turbulence, Hall and inertial effects, as well as collisionless magnetic reconnection.

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arXiv2025

Singular limits of anisotropic weak solutions to compressible magnetohydrodynamics

The aim is to justify rigorously the so-called reduced magnetohydrodynamic model (abbreviated as RMHD), which is widely used in fusion, space and astrophysical plasmas. Motivated by physics, the focus is on plasmas that are simultaneously strongly magnetized and anisotropic. We consider conducting fluids that can be described by viscous and resistive barotropic compressible magnetohydrodynamic equations. The purpose is to study the asymptotic behaviour of global weak solutions, which do exist, for strongly anisotropic plasmas such as the large aspect ratio framework. We prove that such anisotropic weak solutions converge to the weak solutions of the RMHD equations. Rigorous justification of this limit is performed both in a periodic domain and in the whole space. It turns out that the resulting system is incompressible only in the perpendicular direction to the external strong magnetic field, whereas it involves compressible features in the parallel direction. In order to pass to the singular limit in the perpendicular direction we exploit, among others, tools elaborated for proving the low Mach number limit of compressible fluid flows such as the introduction of a fast oscillatory unitary group associated to the dynamics of transverse fast magnetosonic waves. In the parallel direction, we bring out compactness arguments and particular cancellations coming from the structure of our equations.

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arXiv2024

The equations of extended magnetohydrodynamics

Extended magnetohydrodynamics (XMHD) is a fluid plasma model generalizing ideal MHD by taking into account the impact of Hall drift effects and the influence of electron inertial effects. XMHD has a Hamiltonian structure which has received over the past ten years a great deal of attention among physicists, and which is embodied by a non canonical Poisson algebra on an infinite-dimensional phase space. XMHD can alternatively be formulated as a nonlinear evolution equation. Our aim here is to investigate the corresponding Cauchy problem. We consider both incompressible and compressible versions of XMHD with, in the latter case, some additional bulk (fluid) viscosity. In this context, we show that XMHD can be recast as a well-posed symmetric hyperbolic-parabolic system implying pseudo-differential operators of order zero acting as coefficients and source terms. Along these lines, we can solve locally in time the associated initial value problems, with moreover a minimal Sobolev regularity. We also explain the emergence and propagation of inertial waves.

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arXiv2023

The relativistic Vlasov-Maxwell system: Local smooth solvability for weak topologies

This article is devoted to the Relativistic Vlasov-Maxwell system in space dimension three. We prove the local smooth solvability for weak topologies (and its long time version for small data). This result is derived from a representation formula decoding how the momentum spreads, and showing that the domain of influence in momentum is controlled by mild information. We do so by developing a Radon Fourier analysis on the RVM system, leading to the study of a class of singular weighted integrals. In the end, we implement our method to construct smooth solutions to the RVM system in the regime of dense, hot and strongly magnetized plasmas. This is done by investigating the stability properties near a class of approximate solutions.

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arXiv2021

Uniform Lifetime for Classical Solutions to the Hot, Magnetized, Relativistic Vlasov Maxwell System

This article is devoted to the kinetic description in phase space of magnetically confined plasmas. It addresses the problem of stability near equilibria of the Relativistic Vlasov Maxwell system. We work under the Glassey-Strauss compactly supported momentum assumption on the density function $f(t,\cdot)$. Magnetically confined plasmas are characterized by the presence of a strong external magnetic field $ x \mapsto \epsilon^{-1} \mathbf{B}_e(x)$, where $\epsilon$ is a small parameter related to the inverse gyrofrequency of electrons. In comparison, the self consistent internal electromagnetic fields $(E,B) $ are supposed to be small. In the non-magnetized setting, local $ C^1 $-solutions do exist but do not exclude the possibility of blow up in finite time for large data. Consequently, in the strongly magnetized case, since $ \epsilon^{-1} $ is large, standard results predict that the lifetime $T_\epsilon$ of solutions may shrink to zero when $ \epsilon $ goes to $ 0 $. In this article, through field straightening, and a time averaging procedure we show a uniform lower bound ($0<T<T_\epsilon$) on the lifetime of solutions and uniform Sup-Norm estimates. A bootstrap argument allows us to show $f$ remains at a distance $\epsilon$ from the linearized system, while the internal fields can differ by order 1 for well prepared initial data.

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arXiv2019

Turbulent effects through quasi-rectification

This article introduces a physically realistic model for explaining how electromagnetic waves can be internally generated, propagate and interact in strongly magnetized plasmas or in nuclear magnetic resonance experiments. It studies high frequency solutions of nonlinear hyperbolic equations for time scales at which dispersive and nonlinear effects can be present in the leading term of the solutions. It explains how the produced waves can accumulate during long times to produce constructive and destructive interferences which, in the above contexts, are part of turbulent effects.

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arXiv2010

Semiclassical and spectral analysis of oceanic waves

In this work we prove that the shallow water flow, subject to strong wind forcing and linearized around an adequate stationary profile, develops for large times closed trajectories due to the propagation of Rossby waves, while Poincar\'e waves are shown to disperse. The methods used in this paper involve semi-classical analysis and dynamical systems for the study of Rossby waves, while some refined spectral analysis is required for the study of Poincar\'e waves, due to the large time scale involved which is of diffractive type.

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arXiv2009

Trapping Rossby waves

Waves associated to large scale oceanic motions are gravity waves (Poincaré waves which disperse fast) and quasigeostrophic waves (Rossby waves). In this Note, we show by semiclassical arguments, that Rossby waves can be trapped and we characterize the corresponding initial conditions.

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arXiv2004

Cascade of phases in turbulent flows

This article is devoted to incompressible Euler equations (or to Navier-Stokes equations in the vanishing viscosity limit). It describes the propagation of quasi-singularities. The underlying phenomena are consistent with the notion of a cascade of energy.

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