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

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Steinhardt, Paul J.
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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

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2011-06-01
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Suggested Citation: Khoury, J. and Steinhardt, P.J. (2011). Generating scale-invariant perturbations from rapidly-evolving equation of state. Physical Review D. 83, 123502. © 2011 The American Physical Society http://dx.doi.org/10.1103/PhysRevD.83.123502
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