Phenomenology of a pseudo-scalar inflaton: naturally large nongaussianity

By N. Barnaby, R. Namba, Marco Peloso. 2011

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Many controlled realizations of chaotic inflation employ pseudo-scalar axions. Pseudo-scalars are naturally coupled to gauge fields through cF. In the presence of this coupling, gauge field quanta are copiously produced by the rolling inflaton. The produced gauge quanta, in turn, source inflaton fluctuations via inverse decay. These new cosmological perturbations add incoherently with the ``vacuum'' perturbations, and are highly nongaussian. This provides a natural mechanism to generate large nongaussianity in single or multi field slow-roll inflation. The resulting phenomenological signatures are highly distinctive: large nongaussianity of (nearly) equilateral shape, in addition to detectably large values of both the scalar spectral tilt and tensor-to-scalar ratio (both being typical of large field inflation). The WMAP bound on nongaussianity implies that the coupling c of the pseudo-scalar inflaton to any gauge field must be smaller than about 102 Mp−1.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/ef9d97cc27da5cb674393f6bedfefc8e35540905

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Citations in the corpus

Magnetogenesis from axion inflation (2016, methodology): “[52, 58] and further applied and summarized in [59, 60], the backreaction-seeded part of power spectrum can be approximated by”
Planck 2015 results. XVII. Constraints on primordial non-Gaussianity (2015, unknown): “This scenario has a rich and interesting phenomenology both for scalar and tensor primordial fluctuations (see, e.g., Barnaby & Peloso 2011; Sorbo 2011; Barnaby et al. 2011, 2012c; Linde et al. 2013; Meerburg & Pajer 2013; Ferreira & Sloth 2014).”
Primordial gravitational waves for universality classes of pseudoscalar inflation (2016, methodology): “[8, 10, 11], which have served as useful toy-models to illustrate many of the relevant effects.”
Gauge field production in supergravity inflation: Local non-Gaussianity and primordial black holes (2012, methodology): “As was shown in [30, 31], this can be described (up to backreaction effects to be described in the next section) by using (15).”
Non-Gaussianities and chiral gravitational waves in natural steep inflation (2012, background): “[17, 18, 19, 20] (see also [21]) are however performed in the regime where the backreaction of the gauge field on the rolling inflaton is negligible, and therefore inflation is obtained because V (Φ) (that is otherwise considered to have an arbitrary shape) is sufficiently flat.”
Gauge fields and inflation (2012, background): “The amplitude of gauge fields can hence be large, inducing large non-Gaussianity in curvature perturbations [77, 78, 79].”
Vector dark matter production at the end of inflation (2018, methodology): “To get further intuition, it is often useful to work with the solution obtained via the WKB approximation [9, 10, 23] which we can write as,”
Gauge Field Production in Axion Inflation: Consequences for Monodromy, non-Gaussianity in the CMB, and Gravitational Waves at Interferometers (2011, methodology): “where ~ λ are circular polarization tensors (see [20] for more details) and the annihilation/creation operators of the gauge field obey [ aλ(k), a † λ(k ′) ] = δλλ′δ (3) (k− k′) .”
Adding helicity to inflationary magnetogenesis (2014, background): “One important constraint on the model originates from the requirement that the inhomogeneous magnetic field does not mix too strongly with the fluctuations of the inflaton, leading to a nongaussian component in the metric perturbations that would exceed the limits from Planck [27, 28].”
Gravitational waves at interferometer scales and primordial black holes in axion inflation (2016, background): “B of [41] for the study of the backreaction of the vector field on the background dynamics; to section IV A of [68] and section II of [26] for the computation of the scalar perturbations sourced by the vector modes during inflation; finally, to section V of [68] and to section V of [41] for the comp”
Gauge-preheating and the end of axion inflation (2015, background): “Effects such as non-Gaussianity of the density fluctuations, chiral gravitational waves, and the production of primordial black holes [31, 32, 40–42] place upper-bounds on the strength of the couplings, the most stringent being due to restrictions on the production of primordial black holes at the e”
Particle production during inflation and gravitational waves detectable by ground-based interferometers (2011, background): “Finally, in section 4 we discuss the case of tensor modes produced through a gauge ﬁeld coupled to an axion-like inﬂaton (as discussed in [20, 21] and, in greater detail, in [22]).”
A review of axion inflation in the era of Planck (2013, background): “The shape of the bispectrum is close to the equilateral one [62]: the cosine (as defined in [63]) between the bispectrum from this mechanism and the equilateral template is 0.”
Scale-dependent gravitational waves from a rolling axion (2015, background): “This again would lead to an exceedingly large CMB non-gaussianity [41, 42], and, typically, to a growth of the power spectrum which is constrained by smaller scales CMB experiments [43] and the non observation of primordial black holes [44].”
Observable non-gaussianity from gauge field production in slow roll inflation, and a challenging connection with magnetogenesis (2012, methodology): “From the Einstein equations, one finds the same equations for hij in terms of the physical Ei and Bi as in [18],”