​Hörmander's operators are an important class of linear elliptic-parabolic degenerate partial differential operators with smooth coefficients, which have bee

Hörmander operators are a class of linear second order partial differential operators with nonnegative characteristic form and smooth coefficients, which are u

Maximally subelliptic partial differential equations (PDEs) are a far-reaching generalization of elliptic PDEs. Elliptic PDEs hold a special place: sharp result

This book provides the reader with a gentle path through the multifaceted theory of vector fields, starting from the definitions and the basic properties of vec