197 research outputs found
A No-Go Theorem in String Cosmology
A no-go theorem pertaining to the graceful exit problem in Pre-Big-Bang
inflation is reviewed. It is shown that dilaton self-interactions and string
fluid sources fail to facilitate branch changing necessary to avoid
singularities. A comment on the failure of the higher genus corrections to
induce graceful exit is also included.Comment: 7 pages, latex, no figures, contributed talk at the 6th Canadian
Conference on General Relativity and Relativistic Astrophysics, University of
New Brunswick, Fredericton, NB, May 24-2
Topological Mass Generation in Three-Dimensional String Theory
The effective action of string theory in three dimensions is investigated,
incorporating the Lorentz and gauge Chern-Simons terms in the definition of the
Kalb-Ramond axion field strength. Since in three dimensions any three-form is
trivial, the action can be reformulated by properly integrating the axion out.
The circumstances under which it can be recast in form of topologically massive
gravity coupled to a topologically massive gauge theory are pointed out.
Finally, the strong coupling limit of the resulting action is inspected, with
the focus on the roles played by the axion and dilaton fields.Comment: 11 pages LaTeX, Alberta preprint Alberta-Thy-46-9
A Closed Bianchi I Universe in String Theory
A special Bianchi I universe is constructed in string theory.
Geometrically it represents a anti-de-Sitter space crossed with a flat
direction whereas in terms of an associated conformal field theory it is an
extremal case of a gauged WZWN theory with target the coset . Some of its properties are discussed.Comment: 9 pages plain TeX (More typos corrected, a reference added in Ref.
[3], and a new equation (Eq. 7) and some clarifications included
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