Loop-Induced Stochastic Bias at Small Wavevectors

TL;DR

This paper investigates how quantum loop effects during inflation can induce stochastic bias in galaxy distributions at large scales, providing a new mechanism beyond primordial non-Gaussianities for observable large-scale structure features.

Contribution

It introduces a novel mechanism where infrared quantum loop effects generate stochastic bias at small wavevectors, expanding understanding of non-Gaussianity sources in inflation.

Findings

Loop effects lead to observable stochastic bias in galaxy power spectra.

Infrared behavior of quantum loops significantly impacts large-scale structure.

The mechanism is relevant in the context of quasi-single field inflation.

Abstract

Primordial non-Gaussianities enhanced at small wavevectors can induce a power spectrum of the galaxy overdensity that differs greatly from that of the matter overdensity at large length scales. In previous work, it was shown that "squeezed" three-point and "collapsed" four-point functions of the curvature perturbation $\zeta$ can generate these non-Gaussianities and give rise to so-called scale-dependent and stochastic bias in the galaxy overdensity power spectrum. We explore a third way to generate non-Gaussianities enhanced at small wavevectors: the infrared behavior of quantum loop contributions to the four-point correlations of $\zeta$. We show that these loop effects lead to stochastic bias, which can be observable in the context of quasi-single field inflation.