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Viscous stability of quasi-periodic tori
Published online by Cambridge University Press: 27 November 2012
Abstract
This paper is devoted to the study of $P$-regularity of viscosity solutions
$u(x,P)$,
$P\in {\Bbb R}^n$, of a smooth Tonelli Lagrangian
$L:T {\Bbb T}^n \rightarrow {\Bbb R}$ characterized by the cell equation
$H(x,P+D_xu(x,P))=\overline {H}(P)$, where
$H: T^* {\Bbb T}^n\rightarrow {\Bbb R}$ denotes the Hamiltonian associated with
$L$ and
$\overline {H}$ is the effective Hamiltonian. We show that if
$P_0$ corresponds to a quasi-periodic invariant torus with a non-resonant frequency, then
$D_xu(x,P)$ is uniformly Hölder continuous in
$P$ at
$P_0$ with Hölder exponent arbitrarily close to
$1$, and if both
$H$ and the torus are real analytic and the frequency vector of the torus is Diophantine, then
$D_xu(x,P)$ is uniformly Lipschitz continuous in
$P$ at
$P_0$, i.e., there is a constant
$C\gt 0$ such that
$\|D_xu(\cdot ,P)-D_xu(\cdot ,P_0)\|_{\infty }\le C\|P-P_0\|$ for
$\|P-P_0\|\ll 1$. Similar P-regularity of the Peierls barriers associated with
$L(x,v)- \langle P,v \rangle $is also obtained.
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- Copyright © 2012 Cambridge University Press