Non-Gaussianities and chiral gravitational waves in natural steep inflation

Abstract

In [1], we have proposed a model where natural inflation is realized on a steep potential (V (φ) ∼ cos(φ/f ) with f M P ) as a consequence of the interaction of the inflaton with gauge fields through the coupling φ F µνF µν . In the present work we study the nongaussianities and the spectrum of tensor modes generated in this scenario. The nongaussianities turn out to be compatible with current observations and can be large enough to be detectable by Planck. The non-observation of tensor modes imposes new constraints on the parameter space of the system that are about one order of magnitude stronger than those found in [1]. More importantly, in certain regions of the parameter space tensor modes might be detected by upcoming Cosmic Microwave Background experiments even if inflation occurs at energies as low as the TeV scale. In this case the tensor modes would be chiral, and would lead to distinctive parity-violating correlation functions in the CMB.

PBH dark matter from axion inflation

“…In particular we show that a generic higher-dimensional coupling between the inflaton and the gauge fields introduces an instability in the theory, which leads to an exponential production of the gauge fields [28][29][30]. Interestingly this effect induces a back-reaction both on the background dynamics [31,62,63] and on the perturbations [33,38], leading to a wide set of observational consequences. Let us consider the action for a pseudo-scalar inflaton φ, which is coupled to a certain number N of Abelian gauge fields A a µ (associated to U (1) gauge symmetries, 6 i.e.…”

“…A detailed study of the (p)reheating process could also provide interesting clues for the generation of the baryon asymmetry of the 38 Or if N = 1 but the related gauge field is not the Standard Model hypercharge.…”

“…In our case, the fluctuations are characterized by a strong equilateral non-Gaussianity [38], and can in particular be expressed as ζ = g 2 − g 2 with g ∝ ( E · B) 1/2 following a Gaussian distribution (see Eq. B.3) [33].…”

de Sitter symmetries and inflationary correlators in parity violating scalar-vector models

“…We consider a scenario with a scalar field driving the inflationary expansion, and a vector field, which is partly responsible fro the generation of the primordial curvature perturbation and is a source of statistical anisotropies. Several models of this type has been studied in the literature [32,35,37,38,40,[43][44][45][46][47][48][49][50][51][52][53][54][55][56]. The interest for those models has been diverse and it has evolved over the years.…”

“…It is worthwhile to mention the Ratra model [32], which has a rich and interesting phenomenology in the context of primordial magnetogenesis scenario [36,[57][58][59][60] and later used as a source of sizable statistical anisotropies which doesn't dilute with the inflationary evolution [29,[33][34][35]37]. Aside of this, there is a rich literature about models whit an axion/pseudoscalar coupling of the form φFF which allows for interesting phenomenology and source of nonvacuum gravitational waves, chiral gravitational waves, large tensor non-gaussianities among other interesting effects [38,47,49,52,55]. In this paper we consider a mixture of this two scenarios which can be encompassed in the following model:…”