String gas cosmology

Battefeld, Thorsten; Watson, Scott

doi:10.1103/revmodphys.78.435

Cited by 209 publications

(244 citation statements)

References 98 publications

Supporting

Mentioning

242

Contrasting

Order By: Relevance

“…While attempts to construct alternative proposals to inflation in string gas cosmology, such as in [204], are still subject to unsolved problems [151]. [19,205,206], it was shown in a series of recent articles [66,[207][208][209]] that a string gas can be used successfully to describe the matter content in a Hagedorn phase, while providing the possibility of violating the NEC in a controlled manner in string theory. Based on this idea, a cosmological model has been constructed and cosmological perturbations were computed in [202].…”

Section: Instabilitiesmentioning

confidence: 99%

“…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 Hagedorn phase in string-gas cosmology In a speculative, yet interesting proposal motivating the above S-brane bounce, Brandenberger, Vafa and Nayeri [388,389] (see [19,387] for reviews and [206,390] for criticisms) attempted to generate a scale-invariant spectrum of density fluctuations via temperature fluctuations during a quasi-static Hagedorn phase of a string gas comprised of closed heterotic strings 21 . If the dilaton and all other moduli fields are assumed to be stabilized at these high temperatures, the resulting spectrum is indeed scale invariant.…”

Section: Models Based On T-duality In String Theorymentioning

confidence: 99%

See 2 more Smart Citations

A critical review of classical bouncing cosmologies

2015

View full text Add to dashboard Cite

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.

show abstract

Section: Instabilitiesmentioning

confidence: 99%

Section: Models Based On T-duality In String Theorymentioning

confidence: 99%

Section: Models Based On T-duality In String Theorymentioning

confidence: 99%

See 1 more Smart Citation

A critical review of classical bouncing cosmologies

2015

View full text Add to dashboard Cite

show abstract

“…String gas cosmology (SGC) [1,2] (see also [3] for early work, [4,5] for recent overviews, and [6] for a critical review) is an approach to string cosmology, based on adding minimal but crucial inputs from string theory, namely new degrees of freedom -string oscillatory and winding modes -and new symmetries -T-duality -to the now standard hypothesis of a hot and small early universe (see [7] for other work on string gas cosmology, and in particular [8] for a discussion of the role which D-branes play in this scenario). One key aspect of SGC is that the temperature cannot exceed a limiting temperature, the Hagedorn temperature T H [9].…”

Section: Introductionmentioning

confidence: 99%

String Gas Cosmology and Structure Formation

Brandenberger

Nayeri

Patil

et al. 2007

Int. J. Mod. Phys. A

137

172

View full text Add to dashboard Cite

It has recently been shown that a Hagedorn phase of string gas cosmology may provide a causal mechanism for generating a nearly scale-invariant spectrum of scalar metric fluctuations, without the need for an intervening period of de Sitter expansion. A distinctive signature of this structure formation scenario would be a slight blue tilt of the spectrum of gravitational waves. In this paper we give more details of the computations leading to these results.

show abstract

“…via the proposal of [32]. In the effective four-dimensional action, the radion b(t) is replaced by a canonically normalized scalar field ϕ(t) which is related to b(t) through [33,34] …”

Section: The Modelmentioning

confidence: 99%

Predictions of dynamically emerging brane inflation models

Battefeld¹,

Shuhmaher²

2006

Phys. Rev. D

Self Cite

View full text Add to dashboard Cite

We confront the recent proposal of Emerging Brane Inflation with WMAP3+SDSS, finding a scalar spectral index of ns = 0.9659 +0.0049 −0.0052 in excellent agreement with observations. The proposal incorporates a preceding phase of isotropic, non accelerated expansion in all dimensions, providing suitable initial conditions for inflation. Additional observational constraints on the parameters of the model provide an estimate of the string scale.A graceful exit to inflation and stabilization of extra dimensions is achieved via a string gas. The resulting pre-heating phase shows some novel features due to a redshifting potential, comparable to effects due to the expansion of the universe itself. However, the model at hand suffers from either a potential over-production of relics after inflation or insufficient stabilization at late times.

show abstract

String gas cosmology

Cited by 209 publications

References 98 publications

A critical review of classical bouncing cosmologies

A critical review of classical bouncing cosmologies

String Gas Cosmology and Structure Formation

Predictions of dynamically emerging brane inflation models

Contact Info

Product

Resources

About