Gravitational wave background from vacuum and thermal fluctuations during axion-like inflation

Abstract

We revisit the framework of axion-like inflation in view of the possibility that the coupling of the inflaton to a non-Abelian topological charge density could lead to the generation of a rapidly thermalizing heat bath. Both dispersive (mass) and absorptive (friction) effects are included. For phenomenologically viable parameters, the system remains in a weak regime of warm inflation (thermal friction $\ll$ Hubble rate). For tensor perturbations we derive an interpolating formula that incorporates both vacuum and thermal production. The latter yields a model-independent frequency shape $\sim f_0^3$ in the LISA window, whose coefficient allows to measure the maximal shear viscosity of the thermal epoch. It is a challenge, however, to find models where the coefficient is large enough to be observable.

32 pages. v2: clarifications added

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Cited by in corpus (20)

• The warm inflation story
• Freezing-In Gravitational Waves
• Observational Constraints on Warm Natural Inflation
• Upper Bound on Thermal Gravitational Wave Backgrounds from Hidden Sectors
• Warm Inflation with the Standard Model
• Maximal temperature of strongly-coupled dark sectors
• Evolution of coupled scalar perturbations through smooth reheating. I. Dissipative regime
• On Sphaleron Heating in the Presence of Fermions
• Update on gravitational wave signals from post-inflationary phase transitions
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• Evolution of coupled scalar perturbations through smooth reheating. II. Thermal fluctuation regime
• No Warm Inflation From a Vanilla Axion
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• Stochastic gravitational wave from graviton bremsstrahlung in inflaton decay into massive spin 3/2 particles
• Inflationary gravitational wave background as a tail effect
• Not So Minimal Warm Inflation
• Classical equipartition dynamics between axions and non-Abelian gauge fields
• Production of Primordial Gravitational Waves in Teleparallel Gravity