Oscillations in the CMB from axion monodromy inflation

By Raphael Flauger, Liam McAllister, E. Pajer, A. Westphal, Gang Xu. 2009

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We study the CMB observables in axion monodromy inflation. These well-motivated scenarios for inflation in string theory have monomial potentials over super-Planckian field ranges, with superimposed sinusoidal modulations from instanton effects. Such periodic modulations of the potential can drive resonant enhancements of the correlation functions of cosmological perturbations, with characteristic modulations of the amplitude as a function of wavenumber. We give an analytical result for the scalar power spectrum in this class of models, and we determine the limits that present data places on the amplitude and frequency of modulations. Then, incorporating an improved understanding of the realization of axion monodromy inflation in string theory, we perform a careful study of microphysical constraints in this scenario. We find that detectable modulations of the scalar power spectrum are commonplace in well-controlled examples, while resonant contributions to the bispectrum are undetectable in some classes of examples and detectable in others. We conclude that resonant contributions to the spectrum and bispectrum are a characteristic signature of axion monodromy inflation that, in favorable cases, could be detected in near-future experiments.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7b3d766171989a7ade13f1e9abfd42fa37cef563

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Citations in the corpus

Planck 2015 results. XVII. Constraints on primordial non-Gaussianity (2015, neutral): “This periodic symmetry can cause resonances during inflation, imprinting logarithmically-spaced oscillations in the power spectrum, bispectrum and beyond (Flauger et al. 2010; Hannestad et al. 2010; Flauger & Pajer 2011).”
Transplanckian axions!? (2015, background): “In any event, gravitational instantons would still give rise to periodic modulations of the potential which could lead to detectable signatures in the primordial power spectrum [54].”
Exploring cosmic origins with CORE: Inflation (2016, background): “The periodic oscillations appearing in axion monodromy [74, 75] belong to this general class of models [267].”
Simple exercises to flatten your potential (2010, background): “A flux version of monodromy inflation has been obtained at the level of effective field theory also in [22,23], and the phenomenology of monodromy inflation was further developed in [25,26].”
F-term axion monodromy inflation (2014, background): “In addition, to prevent strong backreaction of the intermediate flux stretched between the distant NS brane-antibrane pair [19], the whole system has been proposed to be outcast down an overall throat [20].”
Two-field high-scale inflation in a sub-Planckian region of field space (2009, methodology): “This was not investigated in [8, 9], since there was only one f .”
On loops in inflation (2009, background): “Though for standard slow roll inflation the effect was is in practice unobservable it opened the way to formulate alternative theories which predict much higher levels of non-gaussianities (see for example [3, 4, 5, 6, 7, 8, 9, 10, 11, 12]) and are already constrained by existing data [13, 14, 15].”
Cosmology and Fundamental Physics with the Euclid Satellite (2012, background): “These modulations lead to tiny oscillations in the power spectrum of cosmological fluctuations and to large non-Gaussianity (see for instance [489]).”
Inflation and the scale dependent spectral index: prospects and strategies (2010, background): “However, recent developments in string cosmology yield models with n = 2/5, n = 2/3 and n = 1, so we treat n as a continuous quantity [7, 8].”
Inflation and String Theory (2014, background): “A concrete realization of this protective mechanism involves placing an NS5-brane and an anti-NS5-brane in a common warped throat, as discussed in detail in [36].”