Curvature perturbations from stochastic particle production during inflation

Abstract

We calculate the curvature power spectrum sourced by spectator fields that are excited repeatedly and non-adiabatically during inflation. In the absence of detailed information of the nature of spectator field interactions, we consider an ensemble of models with intervals between the repeated interactions and interaction strengths drawn from simple probabilistic distributions. We show that the curvature power spectra of each member of the ensemble shows rich structure with many features, and there is a large variability between different realizations of the same ensemble. Such features can be probed by the cosmic microwave background (CMB) and large scale structure observations. They can also have implications for primordial black hole formation and CMB spectral distortions. The geometric random walk behavior of the spectator field allows us to calculate the ensemble-averaged power spectrum of curvature perturbations semi-analytically. For sufficiently large stochastic sourcing, the ensemble-averaged power spectrum shows a scale dependence arising from the time spent by modes outside the horizon during the period of particle production, in spite of there being no preferred scale in the underlying model. We find that the magnitude of the ensemble-averaged power spectrum overestimates the typical power spectra in the ensemble because the ensemble distribution of the power spectra is highly non-Gaussian with fat tails.

Soft de Sitter Effective Theory

“…Looking forward, the SdSET approach should make identifying universal corrections more straightforward, although a complete demonstration will require a detailed matching calculation. A case for future study where the potential improvements are less obvious is stochastic particle production due to disorder, as calculated in [113,114]. While numerically it was demonstrated that the superhorizon modes undergo a log-normal random walk, showing this JHEP12(2020)041…”

The Generalized OTOC from Supersymmetric Quantum Mechanics—Study of Random Fluctuations from Eigenstate Representation of Correlation Functions

“…These moments are extremely important in the present context of study as all of them semi-classically compute the expressions for all the equal time quantum correlation functions required to study the out-of-equilibrium aspects, such as stochastic effects, disorder, random fluctuations [91], etc., both at infinite and finite temperatures. See References [2,[92][93][94][95][96], where all authors have studied the physical impact of this formalism to describe out-of-equilibrium aspects in various different contexts. Now, let us speak about some applicability issues related to this particular formalism.…”

The First Three Seconds: a Review of Possible Expansion Histories of the Early Universe

“…The survival of nongravitational relics (including, for example and in addition to DM, matterantimatter asymmetry [57,58,59,60,61], primordial magnetic fields [62,63,64,65,66], or effective number of relativistic species [67,68]) will depend on the details of the expansion history and post-inflationary thermalization of radiation. Along with large-scale gravitational effects associated with the expansion history, smaller scale gravitational effects -including horizon-scaled variations of expansion history and associated non-Gaussianities [69,70,71,72,73,74,75,76,77,78], imprints from small-scale clustering of matter [43,79,80], PBHs [81,82,83,84,85,86,87,88,89,90,91,92,93], and gravitational waves resulting from violent nonlinear dynamics [94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105] -provide hope for future observational probes of the time before BBN. All of the above aspects are topics of this paper.…”