A Cosmic Microscope for the Preheating Era

TL;DR

This paper introduces the concept of a 'cosmic microscope' that uses spatially varying light fields to probe the preheating era of the early universe, revealing nonlinear effects on large-scale fluctuations.

Contribution

It identifies a novel effect of preheating on scalar perturbations, transforming Gaussian fluctuations into square waves, and proposes a model consistent with current observations and detectable by future probes.

Findings

Preheating can induce local non-Gaussianity in scalar perturbations.

The 'modulated partial preheating' model aligns with current cosmological data.

Future cosmic probes can potentially detect these nonlinear preheating effects.

Abstract

Light fields with spatially varying backgrounds can modulate cosmic preheating, and imprint the nonlinear effects of preheating dynamics at tiny scales on large scale fluctuations. This provides us a unique probe into the preheating era which we dub the "cosmic microscope.'' We identify a distinctive effect of preheating on scalar perturbations that turns the Gaussian primordial fluctuations of a light scalar field into square waves, like a diode. The effect manifests itself as local non-Gaussianity. We present a model, "modulated partial preheating," where this nonlinear effect is consistent with current observations and can be reached by near future cosmic probes.