Scale-dependent bias due to primordial vector fields

TL;DR

This paper investigates how primordial Gaussian vector fields induce non-Gaussianity and scale-dependent bias in large-scale structures, offering a new method to probe primordial magnetic fields through their impact on cosmic structure formation.

Contribution

It demonstrates that anisotropic stress from primordial vector fields causes non-Gaussianity similar to local-type and establishes a relationship between scale-dependent bias and vector field power spectrum.

Findings

Non-Gaussianity from vector fields resembles local-type non-Gaussianity.

Scale-dependent bias is directly related to the vector field power spectrum.

Primordial magnetic fields lead to a negative effective $f_{NL}$.

Abstract

Anisotropic stress perturbations induced by primordial Gaussian vector fields create non-Gaussianity in curvature perturbations. We found that such non-Gaussianity closely resembles the local-type non-Gaussianity parametrized by $f_{\rm NL}$, and generates scale-dependent bias in large-scale structures. We also found a simple relationship between the scale-dependent bias and the power spectrum of the vector fields. When the vector fields are interpreted as primordial magnetic fields, the effective $f_{\rm NL}$ is shown to be always negative. The scale-dependent bias provides a new approach to probing primordial vector fields.