Constraining Axion Inflation with Gravitational Waves across 29 Decades in Frequency

Journal Article · Mon Apr 27 00:00:00 EDT 2020 · Physical Review Letters

DOI:https://doi.org/10.1103/physrevlett.124.171301· OSTI ID:1800908

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

We demonstrate that gravitational waves generated by efficient gauge preheating after axion inflation generically contribute significantly to the effective number of relativistic degrees of freedom $$N_{\text{eff}}$$. In this work we show that, with existing Planck limits, gravitational waves from preheating already place the strongest constraints on the inflaton’s possible axial coupling to Abelian gauge fields. We demonstrate that gauge preheating can completely reheat the Universe regardless of the inflationary potential. Further, we quantify the variation of the efficiency of gravitational wave production from model to model and show that it is correlated with the tensor-to-scalar ratio. In particular, when combined with constraints on models whose tensor-to-scalar ratios would be detected by next-generation cosmic microwave background experiments, $$\textit{r}$$ ≳ 10^–3, constraints from $$N_{\text{eff}}$$ will probe or rule out the entire coupling regime for which gauge preheating is efficient.

• Research Organization: Krell Institute, Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC); National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); Ministry of Economic Affairs and Digital Transformation of Spain (MINECO); European Unions Horizon 2020
• Grant/Contract Number: FG02-97ER25308; NNX17AG48G; PHY-1719652; SEV-2016-059; 713366; ACI-1548562
• OSTI ID: 1800908
• Journal Information: Physical Review Letters, Vol. 124, Issue 17; ISSN 0031-9007
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

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