Thibaut COUDARCHET

PhD Student

Research group: String Theory

Thesis

"String theory: Supersymmetry breaking, moduli stabilization and cosmological considerations"
Advisor: Hervé Partouche

PhD Defense n Thursday 30th of September at 2pm at Ecole polytechnique in "Amphi Lagarrigue".

Research interests

String theory, supersymmetry breaking, moduli stabilization, cosmology.

Abstract

The purpose of this thesis is to explore various aspects of string theory, a unified theory of matter and all fundamental interactions including gravity. Some useful key ingredients of the theory and its construction are reviewed before investigating three theoretical facets of it. First, a new supersymmetry-breaking mechanism in open-string models is developed and its features are described, commented and put into perspective with other existing mechanisms. Second, one-loop masses acquired by tree-level moduli are studied in a type I string context with N=2 to N=0 breaking of supersymmetry implemented by a Scherk-Schwarz mechanism. Different strategies are used to conclude on the stability or not at one loop of the wide variety of moduli present in the model, from Taylor expansion of the effective potential to the evaluation of genus-1 two-point correlation functions through arguments arising from the duality between the heterotic and type I string. Eventually, in heterotic string models, the backreaction of the one-loop potential generated by supersymmetry breaking on the cosmology is studied. Flat and ever-expanding solutions are looked for in a cold setup while a new process for generating a dark-matter relic density is developed with implementation of finite temperature.

Publications

Coudarchet T, Dudas E, Partouche H.
Geometry of orientifold vacua and supersymmetry breaking.
Journal of High Energy Physics. 2021(7):104.
DOI: 10.1007/JHEP07(2021)104.

Abel S, Coudarchet T, Partouche H.
On the stability of open-string orbifold models with broken supersymmetry.
Nuclear Physics B. 2020;957:115100.
DOI: 10.1016/j.nuclphysb.2020.115100.

Coudarchet T, Heurtier L, Partouche H.
Spontaneous dark-matter mass generation along cosmological attractors in string theory.
Journal of High Energy Physics. 2019(3):117.
DOI: 10.1007/JHEP03(2019)117.

Coudarchet T, Heurtier L, Partouche H.
Spontaneous freeze out of dark matter. 2019 Corfu Summer Institute "School and Workshops on Elementary Particle Physics and Gravity", CORFU 2019, 31 August 2019 - 25 September 2019. Proceedings of Science, Volume 3762019, Article number 136.

Partouche H, Coudarchet T.
Moduli stability in type I string orbifold models.
​2019 Corfu Summer Institute "School and Workshops on Elementary Particle Physics and Gravity", CORFU 2019, 31 August 2019 - 25 September 2019
Proceedings of Science, Volume 3762019, Article number 164.

Coudarchet T, Partouche H.
Quantum no-scale regimes and moduli dynamics.
Nuclear Physics B. 2018;933:134-84.
DOI: 10.1016/j.nuclphysb.2018.06.009.

Coudarchet T, Fleming C, Partouche H.
Quantum no-scale regimes in string theory.
Nuclear Physics B. 2018;930:235-54.
DOI: 10.1016/j.nuclphysb.2018.03.002.

Preprint

Coudarchet T, Partouche H.
One-loop masses of Neumann-Dirichlet open strings and boundary-changing vertex operators.
arXiv:201113725 

Coudarchet T, Partouche H.
Two-point functions of Neumann-Dirichlet open-string sector moduli.
arXiv:201214442