CMB line-of-sight integrators for nearly-isotropic cosmological models

TL;DR

This paper introduces two new computational tools, AniLoS and AniCLASS, for analyzing CMB anisotropies in nearly-isotropic cosmological models, enabling better constraints on superhorizon anisotropies and their implications for cosmology.

Contribution

The paper presents novel line-of-sight integrators tailored for nearly-isotropic models, extending standard methods to include supercurvature modes and providing accessible software implementations.

Findings

Developed AniLoS, a Python package for CMB anisotropy evolution in these models.

Created AniCLASS, an extension of CLASS for efficient computations.

Illustrated potential initial conditions and their effects on CMB signatures.

Abstract

Homogeneous and nearly-isotropic cosmological models are natural extensions of standard Friedmann cosmologies. Constraining their features is crucial, as any detection of their properties would impact our understanding of inflation and the cosmological principle. Since these models evolve as a set of non-interacting scalar, vector, and tensor modes on top of homogeneous and isotropic spacetimes, their imprints on cosmological observables, particularly the CMB, can be obtained using standard line-of-sight methods. This requires (1) that one resorts on Laplacian eigenmodes on spatially curved spaces and (2) that radial functions for these modes are analytically continued to accommodate complex (i.e., supercurvature) wavenumbers. We introduce two line-of-sight integrators implementing the evolution of the CMB anisotropies in these models: \texttt{AniLoS}, a user-friendly and easy to modify \texttt{Python} package, and \texttt{AniCLASS}, an advanced and efficient extension of the Boltzmann solver \texttt{CLASS}. We discuss possible initial conditions that could generate such fluctuations and provide illustrative examples using our codes. This work offers a pathway for leveraging diverse cosmological datasets to constrain superhorizon anisotropies of the late-time universe.