Non-Gaussianities in models with a varying inflaton decay rate

By M. Zaldarriaga. 2003

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We consider the expected level of primordial non-Gaussianities in models in which density perturbations are produced by spatial fluctuations in the decay rate of the inflaton. We consider both the non-Gaussianities resulting from the self-couplings of the field that controls the decay rate as well as from the non-linear relation between field and curvature perturbations. We show that in these scenario non-Gaussianities are of the "local" form, that is well described be the ansatz R =Rg + f_{NL} (Rg^2 - ). This is a consequence of the fact that they were created when modes were already outside the horizon. We show that f_{NL} is naturally of order a few in these models, much larger than what is expected in the standard one field models of inflation (f_{NL}\sim 10^{-2}) and possibly accessible to observations.

Subfields: Astronomy and Astrophysics, Oceanography

View Paper: https://www.semanticscholar.org/paper/0fd6fa16d1dbb62ead669e0cdb89cd59857dfd56

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Citations in the corpus

Planck 2015 results. XVII. Constraints on primordial non-Gaussianity (2015, unknown): “…2009) or from fluctuations in the inflaton decay rate or interactions, as found in modulated (p)reheating and modulated hybrid inflation (Kofman 2003; Dvali et al. 2004a,b; Bernardeau et al. 2004; Zaldarriaga 2004; Lyth 2005; Salem 2005; Lyth & Riotto 2006; Kolb et al. 2006; Cicoli et al. 2012).”
CMB-S4 Science Case, Reference Design, and Project Plan (2019, background): “Any scenario that predicts local non-Gaussianity, together with fluctuations on scales much larger than our observed volume, predicts a probability distribution for our observed f local NL , but many well-motivated scenarios also predict a small mean value; these include the simplest modulated rehea”
A smooth bouncing cosmology with scale invariant spectrum (2007, background): “The same happens in multi-field inflationary models where the out of the horizon evolution dominates the non-Gaussianity [24, 25].”
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].”
Primordial Non-Gaussianity and Bispectrum Measurements in the Cosmic Microwave Background and Large-Scale Structure (2010, methodology): “A numerical evaluation of (III.129) shows (Babich & Zaldarriaga, 2004) that, for an ideal (i.e. noiseless) experiment, adding the polarization signal produces an improvement of a factor ∼ 2 on fNL constraints.”
The (not so) squeezed limit of the primordial 3-point function (2011, methodology): “We have verified this in the multi-DBI models of [33] and in the non-Gaussianities generated by a cubic interaction λδφ(3) of an isocurvature scalar [34](6).”
Non-Gaussianities in single field inflation and their optimal limits from the WMAP 5-year data (2009, background): “These error bars are expected to decrease by a factor of six in the next few years when the data from the Planck satellite will be available [49].”
The shape of non-Gaussianities (2004, background): “Nevertheless the local contribution is dominant because it has time to develop outside the horizon for many Hubble times before the final conversion to density perturbations [18].”
The effective field theory of multifield inflation (2010, methodology): “where the effects on the overall expansion originates mainly from variation in the reheating process [39] or from a new late phase of matter domination as in the curvaton model [23].”
Galaxy Bias and non-Linear Structure Formation in General Relativity (2011, background): “The so-called local kind of non-Gaussianities [25] that can be produced in multifield inflationary models [26, 27] or in the new bouncing cosmology [28] provides an example where σM depends explicitly on the long wavelength amplitude ζ (7).”
Planck 2018 results. IX. Constraints on primordial non-Gaussianity (2019, methodology): “Lastly, we would like to point out that lensing can also contribute to the covariance (Babich & Zaldarriaga 2004).”
On the consistency relation of the three-point function in single-field inflation (2007, methodology): “Starting from Maldacena’s first full computation of the non-Gaussian features in single-field slow roll inflation [1], several alternative models have been proposed that produce a large and in principle detectable level of non-Gaussianities [2]–[4], [6] through different mechanisms for generating de”