Rapid Methods for Modeling Overdensities of Massive Neutrinos and Other Non-Cold Relics

TL;DR

This paper introduces a fast, parallelized numerical framework for modeling the density profiles of massive neutrinos and other non-cold relics in cosmology, aiding the interpretation of gravitational lensing effects on the CMB.

Contribution

The work presents an efficient, adaptable simulation method for neutrino halo profiles that significantly reduces computational time and allows for rapid parameter scanning and inclusion of new physics.

Findings

Results obtained within seconds per simulation

Framework successfully models non-cold relic clustering

Demonstrates flexibility with various cosmological parameters

Abstract

Recent work has highlighted the potentially detectable gravitational-lensing effect of neutrino halos on cosmic-microwave-background (CMB) fluctuations with upcoming instruments like SO, CMB-S4, and CMB-HD. Accurate modeling of neutrino-halo density profiles are essential for making theory predictions of their cosmological effects. Yet, they are computationally intensive, particularly in the nonlinear regime. In this work, we present an efficient numerical framework for computing neutrino profiles based on N-1-body simulations within a flat FRW Universe. Our approach enables highly parallelized, rapid calculations of neutrino trajectories near spherically symmetric dark-matter halos, delivering results within seconds. In addition to neutrinos, we demonstrate an application to model the clustering of other non-cold relics, such as a freeze-in dark-matter component. The framework is flexible in its definitions of cosmological and dark-matter-halo parameters, which can be particularly valuable for rapid-scanning tasks. It can also seamlessly incorporate new physics, as we demonstrate with examples of a time-varying gravitational constant and nonstandard neutrino phase-space distributions.