A Lie Group Structure for Fourier Integral Operators.
Nikolskii spaces were defined by way of translations on and by way of coordinate maps on a differentiable manifold. In this paper we prove that, for functions with compact support in , we get an equivalent definition if we replace translations by all isometries of . This result seems to justify a definition of Nikolskii type function spaces on riemannian manifolds by means of a transitive group of isometries (provided that one exists). By approximation theorems, we prove that - for homogeneous...
Given any compact manifold , we construct a non-empty open subset of the space of -diffeomorphisms and a dense subset such that the centralizer of every diffeomorphism in is uncountable, hence non-trivial.
normal forms are given for singularities of vectorfields on , which are not flat, and for vectorfields on with , the 1-jet of in the origin is a pure rotation, and some higher order jet of attracting or expanding.