Aspects of string-gas cosmology at finite temperature

Bassett, Bruce A.; Borunda, Mónica; Serone, Marco; Tsujikawa, Shinji

doi:10.1103/physrevd.67.123506

Cited by 68 publications

(112 citation statements)

References 49 publications

(82 reference statements)

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“…At the level of the low energy effective description, the condensate of massless states that appears at Tc forms a short-lived, space-filling object, whose lifetime is comparable to the temporal resolution of the EFT and is therefore modeled as a This setup realizes temperature duality (T-duality) of string theory [66,[207][208][209]. The crucial component in this scenario is a thermal string gas, see [188,189] and [19,203,206,[379][380][381][382] for reviews on string gas cosmology and early work: light thermal momentum modes and light thermal winding modes exchange roles via Tduality. Near the critical temperature, new light degrees of freedom appear due to an enhanced symmetry, giving rise to the S-brane which serves as a glue between the two dual thermal phases.…”

Section: Models Based On T-duality In String Theorymentioning

confidence: 99%

A critical review of classical bouncing cosmologies

2015

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Given the proliferation of bouncing models in recent years, we gather and critically assess these proposals in a comprehensive review. The PLANCK data shows an unmistakably red, quasi scaleinvariant, purely adiabatic primordial power spectrum and no primary non-Gaussianities. While these observations are consistent with inflationary predictions, bouncing cosmologies aspire to provide an alternative framework to explain them. Such models face many problems, both of the purely theoretical kind, such as the necessity of violating the NEC and instabilities, and at the cosmological application level, as exemplified by the possible presence of shear. We provide a pedagogical introduction to these problems and also assess the fitness of different proposals with respect to the data. For example, many models predict a slightly blue spectrum and must be fine-tuned to generate a red spectral index; as a side effect, large non-Gaussianities often result.We highlight several promising attempts to violate the NEC without introducing dangerous instabilities at the classical and/or quantum level. If primordial gravitational waves are observed, certain bouncing cosmologies, such as the cyclic scenario, are in trouble, while others remain valid. We conclude that, while most bouncing cosmologies are far from providing an alternative to the inflationary paradigm, a handful of interesting proposals have surfaced, which warrant further research. The constraints and lessons learned as laid out in this review might guide future research.

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Section: Models Based On T-duality In String Theorymentioning

confidence: 99%

A critical review of classical bouncing cosmologies

2015

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“…To make the distinction, we refer to E s ≡ E W + E K + E dust as the energy in the string gas, the thermodynamical component of the total energy. The following phases will be of interest to us [24].…”

Section: A First Pass At Thermodynamicsmentioning

confidence: 99%

Bouncing and cyclic string gas cosmologies

2009

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We show that, in the presence of a string gas, simple higher-derivative modifications to the effective action for gravity can lead to bouncing and cyclic cosmological models. The modifications bound the expansion rate and avoid singularities at finite times. In these models the scale factors can have long loitering phases that solve the horizon problem. Adding a potential for the dilaton gives a simple realization of the pre-big bang scenario. Entropy production in the cyclic phase drives an eventual transition to a radiation-dominated universe. As a test of the Brandenberger-Vafa scenario, we comment on the probability of decompactifying three spatial dimensions in this class of models.

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“…Our discussion of the first (string radius) era is largely a review of results presented in [14,15,31], though we will draw some new conclusions based on the behavior of the dilaton.…”

Section: Equilibrium Cosmology and The Dilatonmentioning

confidence: 99%

Interaction rates in string gas cosmology

Danos¹,

Frey²,

Mazumdar³

2004

Phys. Rev. D

131

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We study string interaction rates in the Brandenberger-Vafa scenario, the very early universe cosmology of a gas of strings. This cosmology starts with the assumption that all spatial dimensions are compact and initially have string scale radii; some dimensions grow due to some thermal or quantum fluctuation which acts as an initial expansion velocity. Based on simple arguments from the low energy equations of motion and string thermodynamics, we demonstrate that the interaction rates of strings are negligible, so the common assumption of thermal equilibrium cannot apply. We also present a new analysis of the cosmological evolution of strings on compact manifolds of large radius. Then we discuss modifications that should be considered to the usual Brandenberger-Vafa scenario. To confirm our simple arguments, we give a numerical calculation of the annihilation rate of winding strings. In calculating the rate, we also show that the quantum mechanics of strings in small spaces is important.

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Aspects of string-gas cosmology at finite temperature

Cited by 68 publications

References 49 publications

A critical review of classical bouncing cosmologies

A critical review of classical bouncing cosmologies

Bouncing and cyclic string gas cosmologies

Interaction rates in string gas cosmology

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