Boosting GWs in Supersolid Inflation

TL;DR

This paper explores how supersolid inflation models can enhance gravitational wave production during inflation, leading to potentially observable signals with a blue-tilted spectrum due to spontaneous symmetry breaking.

Contribution

It introduces a supersolid inflation framework with scalar fields that produce a secondary gravitational wave signal, saturating current experimental bounds.

Findings

Secondary gravitational waves can be efficiently generated during supersolid inflation.

The resulting gravitational wave spectrum is blue-tilted, potentially observable.

The model predicts non-trivial correlations among scalar power spectra.

Abstract

Inflation driven by a generic self-gravitating medium is an interesting alternative to study the impact of spontaneous spacetime symmetry breaking during a quasi de-Sitter phase, in particular the 4-dimensional diffeomorphism invariance of GR is spontaneously broken down to $ISO(3)$. The effective description is based on four scalar fields that describe the excitations of a supersolid. There are two phonon-like propagating scalar degrees of freedom that mix non-trivially both at early and late times and, after exiting the horizon, give rise to non-trivial correlations among the different scalar power spectra. The non-linear structure of the theory allows a secondary gravitational waves production during inflation, efficient enough to saturate the present experimental bound and with a blue-tilted spectral index.