Statistical anisotropy as a consequence of inflation

TL;DR

This paper explores how inflation-induced inhomogeneities lead to statistical anisotropy in the primordial power spectrum, offering a potential observational test of inflationary models influenced by trans-Planckian physics.

Contribution

It demonstrates that quantum vacuum modes during inflation cause statistical anisotropy in the primordial spectrum, linking early universe physics to observable large-scale structures.

Findings

Predicted almost scale-invariant quadrupole anisotropy

Potential observable effects in CMB and large-scale structure

Dependence on trans-Planckian physics assumptions

Abstract

Cosmological inflation remains to be a unique mechanism of generation of plausible initial conditions in the early universe. In particular, it generates the primordial quasiclassical perturbations with power spectrum determined by the fundamental principles of quantum field theory. In this work, we pay attention to the fact that the quasiclassical perturbations permanently generated at early stages of inflation break homogeneity and isotropy of the cosmological background. The evolution of the small-scale quantum vacuum modes on this inhomogeneous background results in statistical anisotropy of the primordial power spectrum, which can manifest itself in the observable large-scale structure and cosmic microwave background. The effect is predicted to have almost scale-invariant form dominated by a quadrupole and may serve as a non-trivial test of the inflationary scenario. Theoretical expectation of the magnitude of this statistical anisotropy depends on the assumptions about the physics in the trans-Planckian region of wavenumbers.