Generating Scale-Invariant Perturbations from Rapidly-Evolving Equation of State

@article{Khoury2011GeneratingSP,
  title={Generating Scale-Invariant Perturbations from Rapidly-Evolving Equation of State},
  author={Justin Khoury and Paul J. Steinhardt},
  journal={Physical Review D},
  year={2011},
  volume={83},
  pages={123502}
}
Recently, we introduced an ekpyrotic model based on a single, canonical scalar field that generates nearly scale-invariant curvature fluctuations through a purely ''adiabatic mechanism'' in which the background evolution is a dynamical attractor. Despite the starkly different physical mechanism for generating fluctuations, the two-point function is identical to inflation. In this paper, we further explore this concept, focusing in particular on issues of non-Gaussianity and quantum corrections… 

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References

SHOWING 1-10 OF 146 REFERENCES
Generation of a scale-invariant spectrum of adiabatic fluctuations in cosmological models with a contracting phase
In pre-big-bang and in ekpyrotic cosmology, perturbations on cosmological scales today are generated from quantum vacuum fluctuations during a phase when the Universe is contracting (viewed in the
Conditions for generating scale-invariant density perturbations
We analyze the general conditions on the equation of state $w$ required for quantum fluctuations of a scalar field to produce a scale-invariant spectrum of density perturbations, including models
Adiabatic ekpyrosis: scale-invariant curvature perturbations from a single scalar field in a contracting universe.
TLDR
This Letter introduces an ekpyrotic model based on a single, canonical scalar field that generates nearly scale-invariant curvature fluctuations through a purely "adiabatic mechanism" in which the background evolution is a dynamical attractor.
Near Scale Invariance with Modified Dispersion Relations
We describe a novel mechanism for generating a nearly scale invariant spectrum of adiabatic perturbations during a non-inflationary stage. It relies on a modified dispersion relation that contains
Construction of nonsingular pre-big-bang and ekpyrotic cosmologies and the resulting density perturbations
We consider the construction of nonsingular Pre-Big-Bang and Ekpyrotic type cosmological models realized by the addition to the action of specific higher-order terms stemming from quantum
Generating Ekpyrotic Curvature Perturbations Before the Big Bang
We analyze a general mechanism for producing a nearly scale-invariant spectrum of cosmological curvature perturbations during a contracting phase preceding a big bang, which can be entirely described
On the Initial Conditions in New Ekpyrotic Cosmology
New Ekpyrotic Cosmology is an alternative scenario of early universe cosmology in which the universe existed before the big bang. The simplest model relies on two scalar fields, whose entropy
Spontaneous Creation of Almost Scale - Free Density Perturbations in an Inflationary Universe
The creation and evolution of energy-density perturbations are analyzed for the "new inflationary universe" scenario proposed by Linde, and Albrecht and Steinhardt. According to the scenario, the
Rapidly-Varying Speed of Sound, Scale Invariance and Non-Gaussian Signatures
We show that curvature perturbations acquire a scale invariant spectrum for any constant equation of state, provided the fluid has a suitably time-dependent sound speed. In order for modes to exit
Cosmological perturbations in a big-crunch-big-bang space-time
A prescription is developed for matching general relativistic perturbations across singularities of the type encountered in the ekpyrotic and cyclic scenarios, i.e., a collision between orbifold
...
1
2
3
4
5
...