Abstract
We explore whether multifield inflationary models make unambiguous predictions for fundamental cosmological observables. Focusing on -quadratic inflation, we numerically evaluate the full perturbation equations for models with 2, 3, and 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 increases. For fields, 95% of our Monte Carlo samples fall in the ranges , , , and for the spectral index, running, tensor-to-scalar ratio, and isocurvature-to-adiabatic ratio, respectively. The expected amplitude of isocurvature perturbations grows with , raising the possibility that many-field models may be sensitive to postinflationary physics and suggesting new avenues for testing these scenarios.
- Received 5 February 2014
DOI:https://doi.org/10.1103/PhysRevLett.112.161302
© 2014 American Physical Society