Stability analysis of chromo-natural inflation and possible evasion of Lyth’s bound

By E. Dimastrogiovanni, Marco Peloso. 2012

138 citations recorded by the source corpus.

We perform the complete stability study of the model of chromo-natural inflation (Adshead and Wyman '12), where, due to its coupling to a SU(2) vector, a pseudo-scalar inflaton chi slowly rolls on a steep potential. As a typical example, one can consider an axion with a sub-Planckian decay constant f. The phenomenology of the model was recently studied (Dimastrogiovanni, Fasiello, and Tolley '12) in the m_g >> H limit, where m_g is the mass of the fluctuations of the vector field, and H the Hubble rate. We show that the inflationary solution is stable for m_g > 2 H, while it otherwise experiences a strong instability due to scalar perturbations in the sub-horizon regime. The tensor perturbations are instead standard, and the vector ones remain perturbatively small. Depending on the parameters, this model can give a gravity wave signal that can be detected in ongoing or forthcoming CMB experiments. This detection can occur even if, during inflation, the inflaton spans an interval of size Delta chi = O (f) which is some orders of magnitude below the Planck scale, evading a well known bound that holds for a free inflaton (Lyth '97).

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/be7434ca32d1c5f9c73f54a9bb856754e5cf2f7b

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Citations in the corpus

A review of axion inflation in the era of Planck (2013, methodology): “The stability result of [54] was confirmed by [55], that also presented a complete study of the gravitational waves produced in the model, showing that they are chiral.”
Gauge fields and inflation (2012, background): “6, has not yet appeared in the literature, see however [137, 149].”
Primordial gravitational waves from axion-gauge fields dynamics (2016, background): “With the initial condition √ 2k∆j = 1, √ 2k∂x∆j = i, (j = 1, 2, 3) at x = 2 × 104 [90], we numerically compute ∆i and plot them in figure 5.”