Aspects of non-supersymmetric strings theories or with broken supersymmetry

TL;DR

This thesis explores non-supersymmetric string theories, including their constructions, mechanisms of supersymmetry breaking, and cosmological implications, with a focus on time-dependent solutions and alternative inflation models.

Contribution

It provides a comprehensive review of non-supersymmetric string theories, their breaking mechanisms, and cosmological applications, including novel time-dependent solutions.

Findings

Analysis of anomaly cancellation in non-supersymmetric strings

Discussion of string-inspired cosmological models

Presentation of time-dependent solutions in non-supersymmetric string theories

Abstract

The first part of this thesis is a general introduction to the bosonic and fermionic string theory, to the concept of D brane and to string dualities. A discussion of anomalies cancellation closes the chapter. The second part of the thesis reviews the basics of orientifold and orbifold constructions and the Scherk-Schwarz mechanism of supersymmetry breaking. The last part starts with an introduction to standard cosmology and inflation. Alternatives to inflation inspired from string theory and time dependent orbifolds are discussed. Finally time dependent solutions of non-supersymmetric strings are presented.