This introduction to semi-classical analysis is an extension of a course
given by the author at the University of Nankai. It presents for some of
the standard cases presented in quantum mechanics books a rigorous study
of the tunneling effect, as an introduction to recent research work. The
book may be read by a graduate student familiar with the classic book of
Reed-Simon, and for some chapters basic notions in differential
geometry. The mathematician will find here a nice application of PDE
techniques and the physicist will discover the precise link between
approximate solutions (B.K.W. constructions) and exact eigenfunctions
(in every dimension). An application to Witten's approach for the proof
of the Morse inequalities is given, as are recent results for the
Schrödinger operator with periodic potentials.