Constraining axion inflation with gravitational waves from preheating

Peter Adshead; John T. Giblin; Mauro Pieroni; Zachary J. Weiner

doi:10.1103/PhysRevD.101.083534

paper

Constraining axion inflation with gravitational waves from preheating

arXiv:1909.12842 · doi:10.1103/PhysRevD.101.083534

Abstract

We study gravitational wave production from gauge preheating in a variety of inflationary models, detailing its dependence on both the energy scale and the shape of the potential. We show that preheating into Abelian gauge fields generically leads to a large gravitational wave background that contributes significantly to the effective number of relativistic degrees of freedom in the early universe, $N_{eff}$ . We demonstrate that the efficiency of gravitational wave production is correlated with the tensor-to-scalar ratio, $r$ . In particular, we show that efficient gauge preheating in models whose tensor-to-scalar ratio would be detected by next-generation cosmic microwave background experiments ( $r ≳ 1 0^{- 3}$ ) will be either detected through its contribution to $N_{eff}$ or ruled out. Furthermore, we show that bounds on $N_{eff}$ provide the most sensitive probe of the possible axial coupling of the inflaton to gauge fields regardless of the potential.

arXiv commentv2: 23 pages, 10 figures; matches published version

Constraining axion inflation with gravitational waves from preheating

Abstract

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