Université de GenèveDépartement de Physique ThéoriqueCAP Genève

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

13. December 2022
Cite as: 
P. Klose, M. Laine and S. Procacci, JCAP 12 (2022) 020 [arXiv:2210.11710].
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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 overshadowed by the 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 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.


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