New mechanism for generating density perturbations from inflation

By G. Dvali, A. Gruzinov, M. Zaldarriaga. 2003

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We propose a new mechanism to generate density perturbations in inflationary models. Spatial fluctuations in the decay rate of the inflaton field to ordinary matter lead to fluctuations in the reheating temperature. We argue that in most realistic models of inflation the coupling of the inflaton to normal matter is determined by the vacuum expectation values of fields in the theory. If those fields are light during inflation (this is a generic situation in the minimal models of supersymmetric inflation) they will fluctuate leading to density perturbations through the proposed mechanism. We show that these fluctuations could easily dominate over the ones generated through the standard mechanism. The new scenario has several consequences for inflation model building and observations. The proposed mechanism allows to generate the observed level of density perturbations with a much lower scale of inflation and thus generically predicts a smaller level of gravitational waves. The relation between the slope of the spectrum of the produced density perturbations and the potential of the inflaton field is different from the standard relations obtained in the context of slow roll inflation. Because the field responsible for the fluctuations is not the inflaton, it can have significantly larger self couplings and thus density perturbations could be non-Gaussian. The non-Gaussianity can be large enough to be detectable by CMB and Large Scale Structure observations.

Subfields: Astronomy and Astrophysics, Finance

View Paper: https://www.semanticscholar.org/paper/18fb45a56a7a2c4b0b7618eaaaafd760aa5b44b2

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Citations in the corpus

The bispectrum of galaxies from high-redshift galaxy surveys: Primordial non-Gaussianity and non-linear galaxy bias (2007, background): “…described by equation (2) is predicted in models such as the curvaton scenario (Lyth et al. 2003), models with inhomogeneous reheating (Dvali et al. 2004b,a), multiple field inflationary models (Bernardeau & Uzan 2002) or generically in models where the non-linearities arise from the…”
Cosmology and Fundamental Physics with the Euclid Satellite (2012, background): “Other models generating local non-Gaussianities are the so called modulated reheating models, in which one light field modulates the decay of the inflaton field [443, 687].”
A smooth bouncing cosmology with scale invariant spectrum (2007, background): “Another possibility is that the bouncing phase itself depends on the isocurvature scalar ψ, a sort of “variable bounce” in analogy with the variable decay scenario in inflation [31].”
Inflation and string cosmology (2001, background): “One may also produce adiabatic perturbations by perturbing effective coupling constants, which modulates the process of reheating [38, 39].”
DBI in the sky (2004, background): “inflation, and other non-trivial interactions occurring outside the horizon such as those described in [14, 15 , 16, 17, 18].”
Suppressing the lower multipoles in the CMB anisotropies (2003, background): “We would like to mention also, that there is a new possibility of modulated cosmological perturbations from inflation [44, 45], where one may use a different type of tuning to get desirable spectra from inflation, while leaving the inflaton potential unchanged.”
Inflation, Cosmic Perturbations and Non-Gaussianities (2013, background): “This scenario is known as the modulated reheating [117, 189, 190].”
Cosmological Perturbations From Inhomogeneous Reheating, Freeze-Out, and Mass Domination (2003, background): “for M = constant, this recovers our previous result [ 1 ], where now we are interpreting as”
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).”