Stochastic bias from loops of massive particles during inflation

Michael Mcaneny,Alexander K Ridgway,Mikhail P Solon,Mark B Wise

doi:10.1016/j.physletb.2018.06.026

Michael Mcaneny, Alexander K Ridgway + Show 2 more

Open Access

https://doi.org/10.1016/j.physletb.2018.06.026

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Journal: Physics Letters B	Publication Date: Jun 15, 2018
Citations: 3	License type: cc-by

Affiliation: California Institute of Technology

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 ζ 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 ζ. We show that these loop effects can give the largest contributions to the four-point function of ζ in the collapsed limit and be observable in the context of quasi-single field inflation.

Highlights

The inflationary paradigm [1] proposes an era in the very early universe during which the energy density is dominated by vacuum energy and the universe undergoes exponential expansion
The quantum fluctuations in the Goldstone mode π associated with the breaking of time translation invariance by the inflaton [2] source the energy density fluctuations
We find that the infrared region of loop integrals can induce sizable stochastic bias on large scales without introducing any scale-dependent bias

Summary

INTRODUCTION

The inflationary paradigm [1] proposes an era in the very early universe during which the energy density is dominated by vacuum energy and the universe undergoes exponential expansion Such a period elegantly explains why the universe is close to flat and the near isotropy of the cosmic microwave background (CMB). A simple realization of such a model is quasi-single field inflation (QSFI) [4] These non-Gaussianities affect the correlation functions of biased tracers of the underlying matter distribution such as galaxies. It was first pointed out in [5] and [6] that the power spectrum of the galaxy overdensity can become greatly enhanced relative to the HarrisonZel’dovich spectrum on large scales if the primordial mass density perturbations are nonGaussian..

LOOP-INDUCED STOCHASTIC BIAS

Λ2 gμν

LOOP-INDUCED STOCHASTIC BIAS IN QUASI-SINGLE FIELD INFLATION

CONCLUDING REMARKS