Abstract
We study primordial non-gaussianity in supersolid inflation. The dynamics of supersolid is formulated in terms of an effective field theory based on four scalar fields with a shift symmetric action minimally coupled with gravity. In the scalar sector, there are two phonon-like excitations with a kinetic mixing stemming from the completely spontaneous breaking of diffeomorphism. In a squeezed configuration, fNL of scalar perturbations is angle dependent and not proportional to slow-roll parameters showing a blunt violation of the Maldacena consistency relation. Contrary to solid inflation, the violation persists even after an angular average and generically the amount of non-gaussianity is significant. During inflation, non-gaussianity in the TSS and TTS sector is enhanced in the same region of the parameters space where the secondary production of gravitational waves is sizeable enough to enter in the sensitivity region of LISA, while the scalar fNL is still within the current experimental limits.
Highlights
We have minimal knowledge of the Universe before radiation domination
The dynamics of supersolid is formulated in terms of an effective field theory based on four scalar fields with a shift symmetric action minimally coupled with gravity
The downside is that primordial non-gaussianity turns out to be very small, and the amplitude of the stochastic background gravitational waves generated during inflation is tiny and out of reach for LISA
Summary
We have minimal knowledge of the Universe before radiation domination. The most convincing solution of the horizon and flatness problems of the hot big bang model is to assume that the Universe had gone through an early phase of accelerated expansion driven by some sort of “matter” (inflaton). When diffeomorphisms are completely broken down to a global group required for the existence of de Sitter background space-time, the fluctuations of the scalar fields around their VEVs can be associated with the phonon-like excitations of a self-gravitating medium with the properties of a supersolid [7,8,9]; the breaking of spatial diffs by a solid-like medium was considered in [10]. The presence of non-adiabatic perturbations and anisotropic stress of the solid component of the medium leads to violation of the Weinberg theorem In this sense, the option of inflating and forgetting is not available and reheating must be taken into account to determine the seed of primordial perturbations to be used at large scales as initial conditions for the standard radiation dominated phase of the Universe’s evolution.
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