Almost periodic pseudodifferential operators and Gevrey classes
  We study almost periodic pseudodifferential operators acting on almost periodic functions $G_{\rm ap}^s(\rr d)$ of Gevrey regularity index $s \geq 1$. We prove that almost periodic operators with symbols of H\"ormander type $S_{\rho,\delta}^m$ satisfying an $s$-Gevrey condition are continuous on $G_{\rm ap}^s(\rr d)$ provided $0 < \rho \leq 1$, $\delta=0$ and $s \rho \geq 1$. A calculus is developed for symbols and operators using a notion of regularizing operator adapted to almost periodic Gevrey functions and its duality. We apply the results to show a regularity result in this context for a class of hypoelliptic operators. 
Alessandro Oliaro, Luigi Rodino, Patrik Wahlberg
math.FA math.AP