Beyond gevrey regularity: Superposition and propagation of singularities
Beyond gevrey regularity: Superposition and propagation of singularities
We propose the relaxation of Gevrey regularity condition by using sequences which depend on two parameters, and define spaces of ultradifferentiable functions which contain Gevrey classes. It is shown that such a space is closed under superposition, and therefore inverse closed as well. Furthermore, we study partial differential operators whose …