Sharp spectral stability for a class of singularly perturbed pseudo-differential operators

Horia D. Cornean, Radu Purice

Let $a(x,\xi )$ be a real Hörmander symbol of the type $S_{0,0}^0({\mathbb{R}}^d\times {\mathbb{R}}^d)$, let $F$ be a smooth function with all its derivatives globally bounded, and let…