Singular string solutions with nonsingular initial data

These lecture notes provide a short review of the status of time dependent backgrounds in String theory, and in particular those that contain space-like singularities. Despite considerable efforts, we do not have yet a full and compelling picture of such backgrounds. We review some of the various attempts to understand these singularities via generalizations of the BKL dynamics, using worldsheet methods and using non-perturbative tools such as the AdS/CFT correspondence and M(atrix) theory. These lecture notes are based on talks given at Cargese 06 and the dead-sea conference 06.

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“…The boost [17,18,19]. To define the orbifold one first writes Minkowski spacetime in lightcone coordinates,…”

Section: Misner and Grant Spacesmentioning

confidence: 99%

A Short Review of Time Dependent Solutions and Space-like Singularities in String Theory

Berkooz

Reichmann

2007

Nuclear Physics B - Proceedings Supplements

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“…For other studies of orbifolds with CCC's, where an analogous study of unitarity can in principle be done, see [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32].…”

Section: The Orbifoldmentioning

confidence: 99%

Unitarity in the presence of closed timelike curves

Costa

2006

Fortschritte der Physik

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We conjecture that, in certain cases, quantum dynamics is consistent in the presence of closed timelike curves. We consider time dependent orbifolds of three dimensional Minkowski space describing, in the limit of large AdS radius, BTZ black holes inside the horizon. Although perturbative unitarity fails, we show that, for discrete values of the gravitational coupling, particle propagation is consistent with unitarity. This quantization corresponds to the quantization of the black hole angular momentum, as expected from the dual CFT description. Note, however, that we recover this result by analyzing the physics inside the horizon and near the singularity. The spacetime under consideration has no AdS boundary, and we are therefore not using any assumption regarding a possible dual formulation. We perform the computation at very low energies, where string effects are irrelevant and interactions are dominated by graviton exchange in the eikonal regime. We probe the non-causal structure of space-time to leading order, but work to all orders in the gravitational coupling.

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“…This fact was noted already in [34,40]. A natural way to cure the problem is to consider wave functions which are given by linear superpositions of the above basic solutions with different values of p. The problem is then to understand if general perturbations in the far past t ≪ −E −1 will evolve into the future and create an infinite energy density on the horizon, thus destabilizing the geometry.…”

Section: Near Horizon Behaviour Of the Wave Functionsmentioning

confidence: 99%

On the classical stability of orientifold cosmologies

Cornalba

Costa

2003

Class. Quantum Grav.

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We analyze the classical stability of string cosmologies driven by the dynamics of orientifold planes. These models are related to timedependent orbifolds, and resolve the orbifold singularities which are otherwise problematic by introducing orientifold planes. In particular, we show that the instability discussed by Horowitz and Polchinski for pure orbifold models is resolved by the presence of the orientifolds. Moreover, we discuss the issue of stability of the cosmological Cauchy horizon, and we show that it is stable to small perturbations due to in-falling matter.

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Singular string solutions with nonsingular initial data

Cited by 119 publications

References 10 publications

A Short Review of Time Dependent Solutions and Space-like Singularities in String Theory

A Short Review of Time Dependent Solutions and Space-like Singularities in String Theory

Unitarity in the presence of closed timelike curves

On the classical stability of orientifold cosmologies

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