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Inflation in DBI models with constant gamma
Astrophysics · Submitted 27 Nov 2007
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim This paper describes such models in general and presents some examples with a constant speed of sound $c_s<1$ for which the spectrum of scalar perturbations can be found analytically without resorting to the slow roll approximation.
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The abstract, sentence by sentence
Dirac-Born-Infeld scalar field theories which appear in the context of inflation in string theory in general have a field dependent speed of sound. It is however possible to write down DBI models which possess exact solutions characterized by a constant speed of sound different from unity. This requires that the potential and the effective D-brane tension appearing in a DBI action have to be related in a specific way. This paper describes such models in general and presents some examples with a constant speed of sound $c_s<1$ for which the spectrum of scalar perturbations can be found analytically without resorting to the slow roll approximation.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Dirac-Born-Infeld scalar field theories which appear in the context of inflation in string theory in general have a field dependent speed of sound. | background 1.00 | 0.06 | 0.04 | asserted 0.99 |
| s1 | It is however possible to write down DBI models which possess exact solutions characterized by a constant speed of sound different from unity. | contribution 0.40 | 0.44 | 0.30 | hedged possibility 0.94 |
| s2 | This requires that the potential and the effective D-brane tension appearing in a DBI action have to be related in a specific way. | background 0.39 | 0.29 | 0.12 | asserted 1.00 |
| s3 | This paper describes such models in general and presents some examples with a constant speed of sound $c_s<1$ for which the spectrum of scalar perturbations can be found analytically without resorting to the slow roll approximation. | contribution 1.00 | 0.94 | 0.70 | asserted 1.00 |
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The paper
Original abstract
Dirac-Born-Infeld scalar field theories which appear in the context of inflation in string theory in general have a field dependent speed of sound. It is however possible to write down DBI models which possess exact solutions characterized by a constant speed of sound different from unity. This requires that the potential and the effective D-brane tension appearing in a DBI action have to be related in a specific way. This paper describes such models in general and presents some examples with a constant speed of sound $c_s<1$ for which the spectrum of scalar perturbations can be found analytically without resorting to the slow roll approximation.
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References
How the literature uses it
7 arXiv papers cite this in 17 sentences
Papers citing it · 13 sentences without a confident label
Compares with it 1 paper
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For $γ≠1$, the scale factor also evolves as a power law, as can be seen from $H ≡(ȧ / a)$, and Eq. ([ref]) expressed in terms of $ϵ$ as follows: [equation] We then have [equation] with solution [equation] and [equation] This solution was also obtained by Spalinski [ref] , and represents a rescaling of the canonical power-law inflation case.
Quantum modes in DBI inflation: exact solutions and constraints from vacuum selection · Case 2: $ϵ≠0$, $s = 0$ · 0.87
Cites it as background 3 papers
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The DBI inflation with constant speed of sound [ref] as well as with a variable speed of sound has been extensively studied both in the context of slow-roll conditions and beyond [ref] .
Dirac Born-Infeld inflation under constant roll conditions · Introduction · 0.95
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For interesting cosmological aspects of the DBI inflation, see Refs. [ref] .
Anisotropic constant-roll inflation for the Dirac-Born-Infeld model · Introduction · 1.00
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It is worth recalling that a DBI inflationary model with constant (and low) speed of sound has been discussed in [ref] ; also, another k-essence model with constant speed of sound different from unity has also been discussed in [ref] ].
DBI analog of a decaying vacuum cosmology · A particular case: $c_s$ constant and $Λ= 3βH^2$ · 0.96
What it cites · 30 sentences without a confident label
Builds on 4 papers
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The examples discussed are the constant potential (i.e. de Sitter space), the exponential potential[This solution appears in the recent paper by Chimento and Lazkoz [ref] and is a special case of power law inflation in models of k-inflation [ref] .] (leading to power law inflation) and the model introduced by Easther [ref] .
Perturbations in k-inflation · Introduction · 0.85
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The examples discussed are the constant potential (i.e. de Sitter space), the exponential potential[This solution appears in the recent paper by Chimento and Lazkoz [ref] and is a special case of power law inflation in models of k-inflation [ref] .] (leading to power law inflation) and the model introduced by Easther [ref] .
An Inflationary Model with an Exact Perturbation Spectrum · Introduction · 0.85
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The examples discussed are the constant potential (i.e. de Sitter space), the exponential potential[This solution appears in the recent paper by Chimento and Lazkoz [ref] and is a special case of power law inflation in models of k-inflation [ref] .] (leading to power law inflation) and the model introduced by Easther [ref] .
Bridging geometries and potentials in DBI cosmologies · Introduction · 0.85
Uses the method or tool of 1 paper
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As explained in [ref] the correct way to proceed in this case is to define the power spectrum by 𝒫_S(k) = |u_k/z|^2 in the limit of $y→0$.
Horizon crossing and inflation with large \eta · Introduction · 0.95
Uses data or values from 2 papers
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One can also ask what level of tensor perturbations is to be expected from gamls; assuming $n_S≈0.96$ one finds $r=0.32$ for $=0$, dropping to $0.01$ for $=332$ (the current limit [ref] ).
Limits on f_NL parameters from WMAP 3yr data · Introduction · 0.94
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The WMAP3 analysis [ref] favours $n_S - 1 ≈0.96$ if negligible tensor perturbations are assumed.
Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology · Introduction · 0.88
Compares with 1 paper
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For comparison, the corresponding equation for a canonical inflaton [ref] – [ref] is hjcan 3 H^2(ϕ) - V(ϕ) = 2 M_P^4 H'^2 (ϕ) .
A Hamilton-Jacobi approach to non-slow-roll inflation · Introduction · 0.97
Cites as background 10 papers
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The perturbation spectra for all models of this type were subsequently found by Garriga and Mukhanov [ref] .
Perturbations in k-inflation · Introduction · 0.87
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Nonlinear scalar field theories of the Dirac-Born-Infeld type [ref] - [ref] have attracted much attention in recent years due to their role in models of inflation based on string theory [ref] .
Running Non-Gaussianities in DBI Inflation · Introduction · 1.00
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Nonlinear scalar field theories of the Dirac-Born-Infeld type [ref] - [ref] have attracted much attention in recent years due to their role in models of inflation based on string theory [ref] .
Brane Inflation · Introduction · 1.00
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