Scale-dependent gravitational waves from a rolling axion

By R. Namba, Marco Peloso, M. Shiraishi, L. Sorbo, C. Unal. 2015

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We consider a model in which a pseudo-scalar field σ rolls for some e-folds during inflation, sourcing one helicity of a gauge field. These fields are only gravitationally coupled to the inflaton, and therefore produce scalar and tensor primordial perturbations only through gravitational interactions. These sourced signals are localized on modes that exit the horizon while the roll of σ is significant. We focus our study on cases in which the model can simultaneously produce (i) a large gravitational wave signal, resulting in observable B-modes of the CMB polarizations, and (ii) sufficiently small scalar perturbations, so to be in agreement with the current limits from temperature anisotropies. Different choices of parameters can instead lead to a localized and visible departure from gaussianity in the scalar sector, either at CMB or LSS scales.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/b203bae814eda59ec6b0877dc73e2f07b301bc85

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Citations in the corpus

Planck 2018 results. IX. Constraints on primordial non-Gaussianity (2019, background): “Its magnitude varies depending on the shape of the axion-gauge coupling, and, in the best-case scenario, the tensor mode can be comparable in size to or dominate the scalar mode (Cook & Sorbo 2013; Namba et al. 2016; Agrawal et al. 2018).”
Planck 2015 results. XVII. Constraints on primordial non-Gaussianity (2015, unknown): “Its magnitude varies depending on the shape of the axion-gauge coupling, and, in the best-case scenario, the tensor mode can be comparable in size to or dominate the scalar mode (Cook & Sorbo 2013; Namba et al. 2016; Agrawal et al. 2018).”
Gravitational waves at interferometer scales and primordial black holes in axion inflation (2016, methodology): “21 The bumps in the primordial scalar and tensor perturbations due to this mechanism add us incoherently to the standard modes from the vacuum, and the total power spectra are given by [39]”
Gravitational wave signatures of inflationary models from Primordial Black Hole dark matter (2017, methodology): “These perturbations are not statistically correlated with the vacuum ones (those produced by the expansion of the universe in the absence of this axion-gauge field coupling), resulting in a primordial scalar power spectrum of the form [58]”
Science with the space-based interferometer LISA. IV: probing inflation with gravitational waves (2016, background): “It is however possible to consider situations where ξ has a transient, resulting into a localized bump in the spectrum of tensors [87, 88].”
Primordial gravitational waves from axion-gauge fields dynamics (2016, background): “This route is exemplified by the work of [119].”
PICO: Probe of Inflation and Cosmic Origins (2019, background): “ergy scale of at least 5 1In some models of inﬂation the one-to-one correspondence between r and the energy scale of inﬂation does not hold because there are additional sources of gravitational waves [32]. However, in these models the signal is highly non-Gaussian and could be distinguished from mod”
Reconstructing the spectral shape of a stochastic gravitational wave background with LISA (2019, background): “[148]) produce SGWB signals amplified at well defined frequencies in the LISA band, well described by the functional form in the third line of Table 1.”