Preheating afterN-flation

Abstract

We study preheating in N -flation, assuming the Marčenko-Pastur mass distribution, equal energy initial conditions at the beginning of inflation and equal axion-matter couplings, where matter is taken to be a single, massless bosonic field. By numerical analysis we find that preheating via parametric resonance is suppressed, indicating that the old theory of perturbative preheating is applicable. While the tensor-to-scalar ratio, the non-Gaussianity parameters and the scalar spectral index computed for N -flation are similar to those in single field inflation (at least within an observationally viable parameter region), our results suggest that the physics of preheating can differ significantly from the single field case.

Inflation and String Theory

“…However, corrections at higher order in g s may be expected to involve actual loops of the light fields, in closer analogy to (5.150 Phenomenology.-A number of authors have studied the signatures of the phenomenological model (5.147), anticipating a microphysical realization: see e.g. [483,[741][742][743][744][745][746][747][748][749][750]. If a quadratic approximation is applicable, then the tensor-to-scalar ratio is given by r ≈ 0.13 (for 60 e-folds of inflation).…”

Preheating after Multi-Field Inflation

“…However, in the presence of hundreds of dephased fields, m ef f never becomes small enough for parametric resonance to occur; heuristically, one could say that χ particles are simply too heavy to be produced. This intuitive argument was verified numerically in [9] 1 within the framework of N -flation, where N ∼ O(10 2 ) fields contribute to preheating. In N -flation the inflatons all oscillate with different frequencies, because their masses are distributed according to the Marcenko-Pastur law; therefore they dephase quickly within the first few oscillations.…”

“…A challenge in many models is to prevent reheating of hidden sectors [7], but even if the inflatons are primarily coupled to standard model fields, little is known about the presence of resonances in setups with more than a few fields [3,8]. In this note I provide an intuitive argument for the suppression of resonances in generic models of inflation with many fields, summarizing results obtained in [9].…”

“…After many oscillations some fields can become in phase again for short intervals, leading again to minor resonances, but these are infrequent and weak. This suppression of resonances is of course entirely absent if an effective single field model is used [9].…”

“…One option is the old theory of reheating with all of its shortcomings, such as potentially incomplete decay of the inflaton with undesirable consequences [9,10]. Of course, one could also attempt to incorporate more matter fields, each of which only coupled to a single inflaton field.…”