2011/01/18 by Justin Khoury, Paul J. Steinhardt
Physics and Astronomy · #Advanced Thermodynamics and Statistical Mechanics #Cosmology and Gravitation Theories #Quantum chaos and dynamical systems #hep-th
paper · pdf · doi:10.1103/physrevd.83.123502
published as Phys.Rev.D83:123502,2011 · 42 pages, 1 figure
arxiv created 2011/01/18 · openalex publication_date 2011/06/01 · arxiv updated 2011/06/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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. We find that the degeneracy with inflation is broken at three-point level: for the simplest case of an exponential potential, the three-point amplitude is strongly scale dependent, resulting in a breakdown of perturbation theory on small scales. However, we show that the perturbative breakdown can be circumvented---and all issues raised in Linde et al. (arXiv:0912.0944) can be addressed---by altering the potential such that power is suppressed on small scales. The resulting range of nearly scale-invariant, Gaussian modes can be as much as 12 e-folds, enough to span the scales probed by microwave background and large-scale structure observations. On smaller scales, the spectrum is not scale invariant but is observationally acceptable.