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More on the Spectrum of Perturbations in String Gas Cosmology
High Energy Physics - Theory · Submitted 25 Aug 2006
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim It is shown that fixing the dilaton at some early stage is important in order to obtain a scale-invariant spectrum of cosmological fluctuations in string gas cosmology.
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The abstract, sentence by sentence
String gas cosmology is rewritten in the Einstein frame. In an effective theory in which a gas of closed strings is coupled to a dilaton gravity background without any potential for the dilaton, the Hagedorn phase which is quasi-static in the string frame corresponds to an expanding, non-accelerating phase from the point of view of the Einstein frame. The Einstein frame curvature singularity which appears in this toy model is related to the blowing up of the dilaton in the string frame. However, for large values of the dilaton, the toy model clearly is inapplicable. Thus, there must be a new string phase which is likely to be static with frozen dilaton. With such a phase, the horizon problem can be successfully addressed in string gas cosmology. The generation of cosmological perturbations in the Hagedorn phase seeded by a gas of long strings in thermal equilibrium is reconsidered, both from the point of view of the string frame (in which it is easier to understand the generation of fluctuations) and the Einstein frame (in which the evolution equations are well known). It is shown that fixing the dilaton at some early stage is important in order to obtain a scale-invariant spectrum of cosmological fluctuations in string gas cosmology.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | String gas cosmology is rewritten in the Einstein frame. | method 0.55 | 0.78 | 0.03 | asserted 1.00 |
| s1 | In an effective theory in which a gas of closed strings is coupled to a dilaton gravity background without any potential for the dilaton, the Hagedorn phase which is quasi-static in the string frame corresponds to an expanding, non-accelerating phase from the point of view of the Einstein frame. | result 0.93 | 0.66 | 0.18 | asserted 1.00 |
| s2 | The Einstein frame curvature singularity which appears in this toy model is related to the blowing up of the dilaton in the string frame. | result 0.70 | 0.66 | 0.08 | asserted 1.00 |
| s3 | However, for large values of the dilaton, the toy model clearly is inapplicable. | limitation 1.00 | 0.48 | 0.04 | asserted 0.99 |
| s4 | Thus, there must be a new string phase which is likely to be static with frozen dilaton. | interpretation 0.85 | 0.55 | 0.29 | hedged possibility 0.88 |
| s5 | With such a phase, the horizon problem can be successfully addressed in string gas cosmology. | interpretation 0.66 | 0.50 | 0.25 | asserted 0.84 |
| s6 | The generation of cosmological perturbations in the Hagedorn phase seeded by a gas of long strings in thermal equilibrium is reconsidered, both from the point of view of the string frame (in which it is easier to understand the generation of fluctuations) and the Einstein frame (in which the evolution equations are well known). | contribution 0.84 | 0.82 | 0.06 | asserted 0.91 |
| s7 | It is shown that fixing the dilaton at some early stage is important in order to obtain a scale-invariant spectrum of cosmological fluctuations in string gas cosmology. | result 0.99 | 0.87 | 0.41 | asserted 1.00 |
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The paper
Original abstract
String gas cosmology is rewritten in the Einstein frame. In an effective theory in which a gas of closed strings is coupled to a dilaton gravity background without any potential for the dilaton, the Hagedorn phase which is quasi-static in the string frame corresponds to an expanding, non-accelerating phase from the point of view of the Einstein frame. The Einstein frame curvature singularity which appears in this toy model is related to the blowing up of the dilaton in the string frame. However, for large values of the dilaton, the toy model clearly is inapplicable. Thus, there must be a new string phase which is likely to be static with frozen dilaton. With such a phase, the horizon problem can be successfully addressed in string gas cosmology. The generation of cosmological perturbations in the Hagedorn phase seeded by a gas of long strings in thermal equilibrium is reconsidered, both from the point of view of the string frame (in which it is easier to understand the generation of fluctuations) and the Einstein frame (in which the evolution equations are well known). It is shown that fixing the dilaton at some early stage is important in order to obtain a scale-invariant spectrum of cosmological fluctuations in string gas cosmology.
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References
How the literature uses it
26 arXiv papers cite this in 38 sentences
Papers citing it · 32 sentences without a confident label
Contests it 1 paper
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After the conference “Inflation + 25,” where this issue was actively debated, the authors of [ref] issued two new papers reiterating their claims [ref] , but eventually they agreed with our conclusion expressed at this conference: the spectrum of perturbations of the metric in this scenario is blue, with $n = 5$, see Eq. (43) of [ref] .
Inflationary Cosmology · String gas scenario · contest 0.88
Cites it as support 1 paper
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Since we know from [ref] (in the context of vacuum solutions) and [ref] (in the context of string gas matter) that the dilaton increases towards the strong coupling regime in the Big Bang/Crunch region (large tachyon and Hagedorn phases respectively), and thus D-branes become lighter while the fundamental strings become heavier, we will include as matter sources both F-strings and D-strings.
Towards A Nonsingular Tachyonic Big Crunch · Introduction · 0.96
Cites it as background 4 papers
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Several lines of research with different goals have emerged, among them are the stabilization of extra dimensions by massive, classical string gases [ref] or by quantum moduli trapping [ref] , isotropization of large dimensions [ref] , attempts to explain the late time acceleration in the visible dimensions via oscillations of the extra dimensions caused by competition of a stabilizing string gas and matter [ref] , dark matter candidates [ref] , attempts to explain the dimensionality of the observed large dimensions [ref] , bouncing/cyclic cosmologies caused by a coupling of a string gas with a modified gravity action [ref] , and an attempt to provide a non-inflationary explanation of the nearly scale invariant spectrum of scalar perturbations by means of thermal fluctuations during a quasi-static Hagedorn phase [ref] , which is assumed to be directly connected to an expanding, radiation
The Relic Problem of String Gas Cosmology · Introduction · 0.97
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On this basis many alternative cosmological scenarios have been proposed, such as string gas cosmology [ref] , the pre-Big-Bang scenario [ref] , models of Ekpyrotic, cyclic [ref] and bouncing cosmology (see [ref] for a review of older work on bouncing cosmology and [ref] for a review of more recent approaches), and even higher dimensional inflation [ref] .
Defrosting in an Emergent Galileon Cosmology · Introduction · 0.91
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Over the years, this has motivated cosmologists to propose alternatives such as, for example, pre-big bang cosmology [ref] , string gas cosmology [ref] , the ekpyrotic scenario [ref] , and superluminal scenarios [ref] .
DBI Realizations of the Pseudo-Conformal Universe and Galilean Genesis Scenarios · Introduction · 0.98
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