Towards a Cosmological Dual to Inflation

Abstract

We derive all single-field cosmologies with unit sound speed that generate scale invariant curvature perturbations on a dynamical attractor background. We identify three distinct phases: slow-roll inflation; a slowly contracting adiabatic ekpyrotic phase, described by a rapidly-varying equation of state; and a novel adiabatic ekpyrotic phase on a slowly expanding background. All of these yield identical power spectra. The degeneracy is broken at the 3-point level: unlike the nearly gaussian spectrum of slow-roll inflation, adiabatic ekpyrosis predicts large non-gaussianities on small scales.

7 pages, 1 figure. v2: Included section reviewing non-gaussianity calculation, added references

References in corpus (10)

• Starting the Universe: Stable Violation of the Null Energy Condition and Non-standard Cosmologies
• New Ekpyrotic Cosmology
• Galilean Genesis: an alternative to inflation
• Generating Ekpyrotic Curvature Perturbations Before the Big Bang
• Non-Gaussianities in New Ekpyrotic Cosmology
• On the Initial Conditions in New Ekpyrotic Cosmology
• Generating Scale-Invariant Perturbations from Rapidly-Evolving Equation of State
• Near Scale Invariance with Modified Dispersion Relations
• Bimetric structure formation: non-Gaussian predictions
• Seeding of Primordial Perturbations During a Decelerated Expansion

Cited by in corpus (8)

• DBI Realizations of the Pseudo-Conformal Universe and Galilean Genesis Scenarios
• Emergent Universe Scenario via Quintom Matter
• Generating Scale-Invariant Perturbations from Rapidly-Evolving Equation of State
• Non-Gaussianity in single field models without slow-roll
• Scale Invariance via a Phase of Slow Expansion
• Quantum Circuit Complexity of Primordial Perturbations
• Pre-inflationary genesis with CMB B-mode polarization
• Primordial Features as Evidence for Inflation