Physics – High Energy Physics – High Energy Physics - Theory
Scientific paper
2007-12-12
Phys.Rev.D77:066002,2008
Physics
High Energy Physics
High Energy Physics - Theory
27 pages, 6 figures, References added, accepted in PRD
Scientific paper
10.1103/PhysRevD.77.066002
We consider the effects of graviton multiplet fields on transitions between string gas phases. Focusing on the dilaton field, we show that it may obstruct transitions between different thermodynamic phases of the string gas, because the sign of its dimensionally reduced, $T$-duality invariant, part is conserved when the energy density of the universe is positive. Thus, many interesting solutions for which this sign is positive end up in a future curvature singularity. Because of this, some of the thermodynamic phases of the usual gravitating string gases behave like superselection sectors. For example, a past-regular Hagedorn phase and an expanding FRW phase dominated by string momentum modes cannot be smoothly connected in the framework of string cosmology with positive sources. The singularity separates them like a geometric precipice in the moduli space, preventing the dynamics of the theory from bridging across. Sources which simultaneously violate the positivity of energy and NEC could modify these conclusions. We provide a quantitative measure of positivity of energy and NEC violations that would be necessary for such transitions. These effects must dominate the universe at the moment of transition, altering the standard gas pictures. At present, it is not known how to construct such sources from first principles in string theory.
Kaloper Nemanja
Watson Scott
No associations
LandOfFree
Geometric Precipices in String Cosmology does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Geometric Precipices in String Cosmology, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Geometric Precipices in String Cosmology will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-660806