Abstract:Année de publication : 2001
This PhD dissertation contains an account of my works on the non-perturbative structure of the superstring theory. Firstly, I introduce the solitonic p-brane solutions of the supergravity theories. These solutions represented by extended objects of dimension p are generalization of the 't Hooft-Polyakov instantonic solutions to theories with gravitation. Then, the NS1-brane, the solution charged under the Neveu-Schwarz 2-form, corresponding to the superstring is considered as a fundamental object. The connection between these solutions and the non-perturbatives solutions of Dp-branes is exposed. Static and dynamical configurations of D-branes are analyzed in order to understand the structure of the non-perturbative string theory. These results are then applied to study of the non-perturbative correspond between the type~I and SO(32) heterotic string theory, and the self-duality under the Sl(2,Z) group of the type~IIb string. Are deduced precise rules for the instantonic computations are deduce, and a regularization of the ultraviolet divergences of the four gravitons one-loop amplitude computed in the framework of the eleven dimensional supergravity. Which confirms its rôle in the framework of M-theory. A direct computation space-time instantonic contributions for these superstrings theories is done in the new framework of the matrix string theory.