Hybrid inflation with Planck scale fields

Abstract

Observable B-mode polarization in the CMBR would point to a high scale of inflation and large field excursions during the inflationary era. Non-compact string moduli spaces are a suggestive setting for these phenomena. Although they are unlikely to be described by weak coupling models, effective field theories compatible with known features of cosmology do exist. These models can be viewed as generalizations to a large field regime of hybrid inflation. We note close parallels to small and large field axion models. This paper outlines the requirements for successful modular inflation, and gives examples of effective field theories which satisfy them. The required tunings are readily characterized. These models can also be thought of as models of chaotic inflation, in a way we describe. In the modular framework, one would expect that any would-be Peccei-Quinn symmetry would likely be badly broken during inflation, and the axion would have Hubble scale mass; in this situation, isocurvature fluctuations would be suppressed and the initial misalignment angle would be fixed, rather than being a random variable.

Adiabatic suppression of the axion abundance and isocurvature due to coupling to hidden monopoles

“…refs. [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] for other scenarios to suppress the axion isocurvature.…”

Light scalars and the cosmos: Nambu–Goldstone and otherwise

“…Chaotic inflation has, for decades, provided a simple model for slow roll inflation, and its prediction of transplanckian field motion and observable gravitational radiation is compatible with our discussion of large field modular inflation. As we look at the moduli inflation model of the previous section (and more generally moduli models of large field inflation), we see, in fact, a realization of the ideas of chaotic inflation [31]. Again, the potential behaves as…”

“…This model is discussed in the Planck theory paper which rules it out based on their measurement of n s . Suitable modifications are discussed in [31]. A model with similar features (with cosh rather than exponential potential) has been discussed in [35].…”

Isocurvature perturbations of dark energy and dark matter from the Swampland conjecture

“…This leads to isocurvature perturbations for DM, which is severely constrained by the Planck data as we discussed above. Several mechanisms have been proposed to suppress its fluctuations by, e.g., making the axion-like particle massive temporarily during inflation [84][85][86][87][88][89][90][91][92][93][94][95][96][97][98][99][100]. Alternatively, if the Peccei-Quinn symmetry is restored during inflation (or reheating epoch) and gets broken after inflation, there is no large correlation for field perturbations beyond the horizon scale.…”