Decay estimates for large velocities in the Boltzmann equation without cutoff

Abstract : We consider solutions $f=f(t,x,v)$ to the full (spatially inhomogeneous) Boltzmann equation with periodic spatial conditions $x \in \mathbb T^d$, for hard and moderately soft potentials \emph{without the angular cutoff assumption}, and under the \emph{a priori} assumption that the main hydrodynamic fields, namely the local mass $\int_v f(t,x,v)$ and local energy $\int_v f(t,x,v)|v|^2$ and local entropy $\int_v f(t,x,v) \ln f(t,x,v)$, are controlled along time. We establish quantitative estimates of \emph{propagation} in time of pointwise polynomial moments'', i.e. $\sup_{x,v} f(t,x,v) (1+|v|)^q$, $q \ge 0$. In the case of hard potentials, we also prove \emph{appearance} of these moments for all $q \ge 0$. In the case of moderately soft potentials we prove the \emph{appearance} of low-order pointwise moments.

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https://hal.archives-ouvertes.fr/hal-01766669
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Submitted on : Thursday, March 21, 2019 - 8:17:21 PM
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Cyril Imbert, Clément Mouhot, Luis Silvestre. Decay estimates for large velocities in the Boltzmann equation without cutoff. Journal de l'École polytechnique — Mathématiques, École polytechnique, 2020, 7, pp.143-184. ⟨10.5802/jep.113⟩. ⟨hal-01766669v2⟩

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