Simple predictions from multifield inflationary models

Richard Easther; Jonathan Frazer; Hiranya V. Peiris; Layne C. Price

doi:10.1103/PhysRevLett.112.161302

paper

Simple predictions from multifield inflationary models

arXiv:1312.4035 · doi:10.1103/PhysRevLett.112.161302

Abstract

We explore whether multifield inflationary models make unambiguous predictions for fundamental cosmological observables. Focusing on $N$ -quadratic inflation, we numerically evaluate the full perturbation equations for models with 2, 3, and $O (100)$ fields, using several distinct methods for specifying the initial values of the background fields. All scenarios are highly predictive, with the probability distribution functions of the cosmological observables becoming more sharply peaked as $N$ increases. For $N = 100$ fields, 95% of our Monte Carlo samples fall in the ranges $n_{s} \in (0.9455, 0.9534)$ ; $α \in (- 9.741, - 7.047) \times 1 0^{- 4}$ ; $r \in (0.1445, 0.1449)$ ; and $r_{iso} \in (0.02137, 3.510) \times 1 0^{- 3}$ for the spectral index, running, tensor-to-scalar ratio, and isocurvature-to-adiabatic ratio, respectively. The expected amplitude of isocurvature perturbations grows with $N$ , raising the possibility that many-field models may be sensitive to post-inflationary physics and suggesting new avenues for testing these scenarios.

5 pages, 4 figure; v2: minor clarifications and references added; version accepted by Phys. Rev. Letters; v3: minor typo corrected

Simple predictions from multifield inflationary models

Abstract

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