Density perturbations in the Ekpyrotic Universe and string-inspired generalizations

Abstract

We study density perturbations in several cosmological models motivated by string theory. The evolution and the spectra of curvature perturbations $\mathcal{R}$ are analyzed in the Ekpyrotic scenario and nonsingular string cosmologies. We find that these string-inspired models generally exhibit blue spectra in contrast to standard slow-roll inflationary scenarios. We also clarify the parameter range where $\mathcal{R}$ is enhanced on superhorizon scales.

5 pages, 3 figures, some discussions and references are added

References in corpus (5)

• Effects of Cosmological Moduli Fields on Cosmic Microwave Background
• Enhancement of superhorizon scale inflationary curvature perturbations
• Cosmological perturbations from multi-field inflation in generalized Einstein theories
• Evolution of cosmological perturbations in non-singular string cosmologies
• Gravitational waves in non-singular string cosmologies

Cited by in corpus (59)

• Dynamics of dark energy
• Modified Gravity and Cosmology
• Properties of singularities in (phantom) dark energy universe
• Inflation Dynamics and Reheating
• The Pre-Big Bang Scenario in String Cosmology
• Gauss-Bonnet dark energy
• On the Generation of a Scale-Invariant Spectrum of Adiabatic Fluctuations in Cosmological Models with a Contracting Phase
• Ekpyrotic and Cyclic Cosmology
• Dilatonic ghost condensate as dark energy
• Construction of cosmologically viable f(G) gravity models
• A Critical Review of Classical Bouncing Cosmologies
• The fate of (phantom) dark energy universe with string curvature corrections
• On the Construction of Nonsingular Pre-Big-Bang and Ekpyrotic Cosmologies and the Resulting Density Perturbations
• Adiabatic and Isocurvature Perturbations for Multifield Generalized Einstein Models
• Cosmological perturbations through a simple bounce
• Solar system constraints on f(G) gravity models
• Slow-roll inflation with a Gauss-Bonnet correction
• Power spectra from an inflaton coupled to the Gauss-Bonnet term
• Adiabatic perturbations in pre big bang models: matching conditions and scale invariance
• Density perturbations in generalized Einstein scenarios and constraints on nonminimal couplings from the Cosmic Microwave Background
• Cosmological Constraints on $f(G)$ Dark Energy Models
• Inflation coupled to a Gauss-Bonnet term
• Isocurvature perturbations in the Ekpyrotic universe
• Assisted Contraction
• Inflation with Gauss-Bonnet coupling
• Delicate f(R) gravity models with disappearing cosmological constant and observational constraints on the model parameters
• Inflation in string-inspired cosmology and suppression of CMB low multipoles
• Non-singular big-bounces and evolution of linear fluctuations
• Cosmological Perturbations Through a General Relativistic Bounce
• Realizing Scale-invariant Density Perturbations in Low-energy Effective String Theory
• Comment on "Density perturbations in the ekpyrotic scenario"
• Patch dualities and remarks on nonstandard cosmologies
• The Primordial Perturbation Spectrum from Various Expanding and Contracting Phases
• Study of a Class of Four Dimensional Nonsingular Cosmological Bounces
• Collision of Domain Walls and Reheating of the Brane Universe
• Nature of singularities in anisotropic string cosmology
• Regular two-component bouncing cosmologies and perturbations therein
• On Dualities Of Primordial Perturbation Spectra
• Pleasant behavior of swampland conjectures in the face of specific inflationary models
• Superhorizon curvaton amplitude in inflation and pre-big bang cosmology
• Construction of nonsingular cosmological solutions in string theories
• Perturbations in a Bouncing Brane Model
• Primordial Spectra of slow-roll inflation at second-order with the Gauss-Bonnet correction
• On the Transfer of Metric Fluctuations when Extra Dimensions Bounce or Stabilize
• Collision of Domain Walls in asymptotically Anti de Sitter spacetime
• Cosmological density perturbations from perturbed couplings
• General solution for scalar perturbations in bouncing cosmologies
• A Note on the Viability of Gauss-Bonnet Cosmology
• The phase-space of generalized Gauss-Bonnet dark energy
• Identification of perturbation modes and controversies in ekpyrotic perturbations
• The generalized second law of thermodynamics for interacting $f(R)$ gravity
• Cosmological perturbations in the 5D Big Bang
• No-Go theorems for ekpyrosis from ten-dimensional supergravity
• Cosmologies from higher-order string corrections
• Evolution of linear perturbations through a bouncing world model: Is the near Harrison-Zel'dovich spectrum possible via a bounce?
• Early and Late-time Cosmic Acceleration in Non-minimal Yang-Mills-$f(G)$ Gravity
• Scalar Perturbation Spectra in an Emergent Cosmological Island
• Bouncing universes and their perturbations : a simple model revisited
• Modified gravity from an entropy functional