Abstract
In this contribution we discuss the possibility of generating an observable gravitational wave (GW) background by coupling a pseudo-scalar inflaton to some Abelian gauge fields. This analysis is performed by dividing inflationary models into universality classes. We find that of the most promising scenario is a Starobinsky-like model, which may lead to the generation of observational signatures both in upcoming CMB detectors as well as for direct GW detectors. The signal which can be produced in these models would both be observable in ground-based detectors, such as advanced LIGO, and in space-based detectors, such as LISA. The complementarity between the CMB and direct GW detection may be used to extract informations on the microphysics of inflation. Interestingly the mechanism discussed in this contribution may also be relevant for the generation of Primordial Black Holes (PBHs).
Highlights
Inflation is nowadays accepted as a cornerstone of modern cosmology and in particular its simplest realization in terms of single scalar field slow-rolling in its potential appears to match with cosmological observations at CMB scales
Quantum fluctuations of the inflaton field and of the metric are stretched on macroscopic scales by the exponential expansion. This mechanism naturally provides an explanation to the anisotropies in the CMB and it is expected to generate a background of primordial gravitational wave (GW)
This generalized framework leads to a wide set of observational consequences such as: the production of a GW background which can be observed at GW interferometers such as advanced LIGO/VIRGO and LISA [1, 6, 11, 12], the presence of a non-Gaussian component in the scalar power spectrum [6,7,8,9,11,12], the generation of a distribution of Primordial Black Holes (PBHs) [8,11,12] and the generation of μ-distortions [10,11,12]
Summary
Inflation is nowadays accepted as a cornerstone of modern cosmology and in particular its simplest realization in terms of single scalar field slow-rolling in its potential appears to match with cosmological observations at CMB scales. The gauge fields produced with this mechanism induce a back-reaction both on the background dynamics [5, 6] and on the perturbations [7, 8] (both the scalar and tensor power spectra are exponentially enhanced at small scales). In particular we show that because of the exponential enhancement of the tensor spectrum at small scales, GW interferometers may be used to probe different inflationary models.
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