The study of string theory has recently opened the way to many ground-breaking ideas in theoretical physics. An aspect that had been neglected until recently concerns the role played by time in this theory. It is an important subject because of its possible connections with the field of cosmology. In the first part of this thesis we study S(pacelike)D-branes which are objects arising naturally in string theory when Dirichlet boundary conditions are imposed on the time direction. SD-brane physics is inherently time-dependent. We set up the problem of coupling the most relevant open-string tachyonic mode to massless closed-string modes in the bulk, with back-reaction and Ramond-Ramond fields included. We find solutions (numerically) that are asymptotically flat in the future but plagued with a singularity in the past. The second part of the thesis is concerned with the study of important aspects related to the proposed duality between quantum gravity in de Sitter space and a Euclidean eonformal field theory: the dS/CFT correspondence. First, we study solutions of Einstein gravity coupled to a positive cosmological constant and matter which are asymptotically de Sitter and homogeneous. These solutions are 'tall', meaning that the perturbed universe lives through enough eonformal time for an entire spherical Cauchy surface to enter any observer's past light cone. Our main focus is on the implications of tall universes for the correspondence. Particular attention is given to the associated renormalization group flows, leading to a more general de Sitter c-theorem. We also discuss the eonformal diagrams for various classes of homogeneous flows. Then, we consider the evolution of massive scalar fields in (asymptotically) de Sitter spacetimes of arbitrary dimension. Through the dS/CFT correspondence, our analysis points to the existence of new non-local dualities for the eonformal field theory.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.19635 |
| Date | January 2003 |
| Creators | Leblond, Frédéric |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Physics) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002022518, Theses scanned by McGill Library. |
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