Imprints of Reheating Dynamics on Gravitational Waves from Phase Transitions

TL;DR

This paper explores how the reheating process after inflation influences the gravitational wave signals from cosmological phase transitions, revealing suppression effects and unique spectral features tied to the reheating dynamics.

Contribution

It demonstrates that perturbative reheating alters the GW spectrum from phase transitions, introducing suppression and distinctive spectral signatures linked to the inflaton potential.

Findings

GW signals are suppressed during perturbative reheating compared to radiation domination.

Characteristic spectral features can indicate the reheating history.

Reheating dynamics influence the thermodynamic conditions of phase transitions.

Abstract

We investigate how perturbative reheating after inflation modifies the primordial gravitational wave (GW) spectrum generated by cosmological phase transitions. Within a specific inflationary setup, we show that the thermodynamic quantities that control the phase transition depend on the effective equation of state of the cosmological background, which is itself set by the form of the inflaton potential during reheating. Assuming reheating proceeds via perturbative dissipation of the inflaton condensate into boson or fermion pairs, we find that phase transitions taking place in this epoch generally produce GW signals that are systematically suppressed compared with the standard radiation-dominated scenario. We also identify characteristic spectral features that may arise in this case, which could serve as distinctive signatures of the modified expansion history during reheating.