Large Scale Anisotropic Bias from Primordial non-Gaussianity

TL;DR

This paper investigates how primordial anisotropic non-Gaussianity affects large scale structure bias, revealing direction-dependent modifications and specific selection rules in anisotropic inflation models.

Contribution

It introduces a scale-dependent bias formulation for anisotropic inflation, highlighting the directional dependence and extending the theory to general anisotropic primordial conditions.

Findings

Bias amplitude is direction-dependent and vanishes at leading order when aligned with the anisotropic direction.

Selection rules identify which parts of the anisotropic bispectrum influence the bias.

Bias is mainly affected by the angle between the anisotropic direction and the long wavelength mode.

Abstract

In this work we study the large scale structure bias in models of anisotropic inflation. We use the Peak Background Splitting method in Excursion Set Theory to find the scale-dependent bias. We show that the amplitude of the bias is modified by a direction- dependent factor. In the specific anisotropic inflation model which we study, the scale- dependent bias vanishes at leading order when the long wavelength mode in squeezed limit is aligned with the anisotropic direction in the sky. We also extend the scale-dependent bias formulation to the general situations with primordial anisotropy. We find some selection rules indicating that some specific parts of a generic anisotropic bispectrum is picked up by the bias parameter. We argue that the anisotropic bias is mainly sourced by the angle between the anisotropic direction and the long wavelength mode in the squeezed limit.