Integral Formulas Related to Wave Fronts

S.~S.~Anisov

Abstract.

In the first section of the paper we study some properties of oriented
volumes of wave fronts propagating in spaces of constant curvature. In
the second section, we generalize to an arbitrary isometric action of
a Lie group on a Riemannian manifold the following principle: an extra
pression inside of a ball does not move it.