Gaugid inflation

TL;DR

This paper introduces magnetic gaugid inflation, an EFT framework where a triplet of $U(1)$ gauge fields in a magnetic background drives inflation with a distinctive symmetry-breaking pattern. A helicity-2 phonon $E_{ij}$ mixes with the graviton through a single-derivative coupling, significantly modifying the primordial tensor spectrum and decoupling the tensor amplitude from the inflationary Hubble scale to allow sizeable gravitational waves at low scales. The scalar and vector sectors reduce to the same phenomenology as solid inflation, with $ abla$-flow-like scalar dynamics and vector phonons; reheating then determines how the end-of-inflation correlators map to the observed adiabatic perturbations. The model provides a controllable mechanism to enhance or suppress $r$ via the gaugid’s propagation speeds and slow-roll parameters, while permitting a rich set of reheating-dependent predictions and extensions, such as parity-breaking or higher-point functions.

Abstract

The spectrum of primordial gravitational waves is one of the most robust inflationary observables, often thought of as a direct probe of the energy scale of inflation. We present a simple model, where the dynamics controlling this observable is very different than in the standard paradigm of inflation. The model is based on a peculiar finite density phase---the magnetic gaugid---which stems from a highly non-linear effective theory of a triplet of abelian gauge fields. The gaugid extends the notion of homogeneous isotropic solid, in that its spectrum of fluctuations includes helicity-2 phonons. We show how, upon implementing the gaugid to drive inflation, the helicity-2 phonon mixes with the graviton, significantly affecting the size of the primordial tensor spectrum. The rest of the features of the theory, in particular the vector and scalar perturbations, closely resemble those of solid inflation.