Predictions of dynamically emerging brane inflation models

Battefeld, Thorsten; Shuhmaher, Natalia

doi:10.1103/physrevd.74.123501

Cited by 6 publications

(6 citation statements)

References 59 publications

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“…One such framework was proposed in [64,65] (see also [66,67,68] for related work on incorporating inflation by means of brane gases) where anisotropic inflation (as argued for in [69]) is incorporated: the multi-dimensional universe starts out small and hot, with our three dimensions compactified on a torus and the extra dimensions on an orbifold of the same size. The pre-inflationary expansion is governed by topological defects (p-branes) in the bulk [65].…”

Section: B Incorporating Inflationmentioning

confidence: 99%

The relic problem of string gas cosmology

Battefeld

2009

Phys. Rev. D

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We discuss the relic problem of string gas cosmology (SGC) using gravitinos and magnetic monopoles as examples. Since SGC operates near or at the Hagedorn temperature, relics are produced copiously; in the absence of dilution, their abundances are too large. A subsequent phase of reheating can solve the gravitino problem, but fails to dilute monopoles sufficiently. We propose a subsequent phase of inflation as the most natural solution to the monopole problem; unfortunately, inflation marginalizes almost all potential achievements of SGC, with the exception of a possible explanation of the dichotomy of space (why did only three dimensions inflate?).

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Section: B Incorporating Inflationmentioning

confidence: 99%

The relic problem of string gas cosmology

Battefeld

2009

Phys. Rev. D

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“…This proposal works within dilaton gravity and is not necessarily valid in the Hagedorn regime. Furthermore, since string gases redshift like matter, this stabilization mechanism is problematic at late times [476], particularly in the presence of a cosmological constant [477].…”

Section: A Preheating and Reheatingmentioning

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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“…Up until t c the energy in the preheat matter field is increasing, due to the increase of φ to which it is coupled. If no decay channel were open to χ the adiabatic field would bounce back due to backreaction, providing an example of moduli trapping [47,48,49,50,51,52,53,54]. This is not the case here, since χ-particles can decay into Fermions.…”

Section: Ekpyrosismentioning

confidence: 90%

Modulated perturbations from instant preheating after new ekpyrosis

Battefeld

2008

Phys. Rev. D

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We present a mechanism to transfer the spectrum of perturbations in a scalar isocurvature field ξ onto the matter content in the radiation era via modulated, instant preheating after ekpyrosis. In this setup, ξ determines the coupling constant relevant for the decay of a preheat matter field into Fermions. The resulting power spectrum is scale invariant if ξ remains close to a scaling solution in new ekpyrotic models of the universe; by construction the spectrum is independent of the detailed physics near the bounce. The process differs from the curvaton mechanism, which has been used recently to revive the ekpyrotic scenario, in that no peculiar behavior of ξ shortly before or during the bounce is needed. In addition, a concrete and efficient realization of reheating after ekpyrosis is provided; this mechanism is not tied to ekpyrotic models, but could equally well be used in other setups, for instance inflationary ones. We estimate non-Gaussianities and find no additional contributions in the most simple realizations, in contrast to models using the curvaton mechanism.

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Predictions of dynamically emerging brane inflation models

Cited by 6 publications

References 59 publications

The relic problem of string gas cosmology

The relic problem of string gas cosmology

A critical review of classical bouncing cosmologies

Modulated perturbations from instant preheating after new ekpyrosis

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