Kination-like Era Driven by the Effective Inflaton/Higgs Potential

TL;DR

This paper proposes a model where the inflaton field in a $U(1)_X$ extended Standard Model causes a stiff era, leading to a distinctive gravitational wave spectrum that can be tested by future GW detectors and collider experiments.

Contribution

It introduces a novel inflationary scenario driven by the $U(1)_X$ Higgs field with a Coleman-Weinberg potential, predicting a unique GW signature and linking it to collider phenomenology.

Findings

A stiff era with $w > 1/3$ can occur after inflation.

The GW spectrum is significantly modulated and enhanced.

Future GW detectors like U-DECIGO can potentially observe this spectrum.

Abstract

Based on the minimal $U(1)_X$ extended Standard Model, we explore cosmic inflation where the $U(1)_X$ Higgs field serves as the inflaton. We demonstrate that a stiff era with an equation of state $w > 1/3$ can emerge during the inflaton's oscillatory phase after inflation, driven by the Coleman-Weinberg potential of the inflaton, arising due to radiative corrections. This leads to significant modulation and enhancement of the irreducible stochastic gravitational wave (GW) background from inflation, deviating from the conventional scale-invariant spectrum. Such a distinct GW spectrum could be detectable by next-generation GW interferometer missions, such as U-DECIGO. In our framework, the GW spectrum depends on the $U(1)_X$ gauge coupling and the mass of the $U(1)_X$ gauge boson ($Z^\prime$). As a result, future GW observations and $Z^\prime$ boson resonance searches at high-energy collider experiments are complementary to one another.