  This article is concerned with maximal accretive realizations of geometric
Kramers-Fokker-Planck operators on manifolds with boundaries. A general class
of boundary conditions is introduced which ensures the maximal accretivity and
some global subelliptic estimates. Those estimates imply nice spectral
properties as well as exponential decay properties for the associated
semigroup. Admissible boundary conditions cover a wide range of applications
for the usual scalar Kramer-Fokker-Planck equation or Bismut's hypoelliptic
Laplacian.
