Microdifferential operator

In mathematics, a microdifferential operator is a linear operator on a cotangent bundle (phase space) that generalizes a differential operator and appears in the framework of microlocal analysis as well as in the Kyoto school of algebraic analysis. The notion was originally introduced by L. Boutet de Monvel and P. Krée as well as by M. Sato, T. Kawai and M. Kashiwara.