Everything hot everywhere all at once: Neutrinos and hot dark matter as a single effective species

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Main Authors: Upadhye, Amol, Mosbech, Markus R., Pierobon, Giovanni, Wong, Yvonne Y. Y.
Format: Preprint
Published: 2024
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author Upadhye, Amol
Mosbech, Markus R.
Pierobon, Giovanni
Wong, Yvonne Y. Y.
author_facet Upadhye, Amol
Mosbech, Markus R.
Pierobon, Giovanni
Wong, Yvonne Y. Y.
contents Observational cosmology is rapidly closing in on a measurement of the sum M_nu of neutrino masses, at least in the simplest cosmologies, while opening the door to probes of non-standard hot dark matter (HDM) models. By extending the method of effective distributions, we show that any collection of HDM species, with arbitrary masses, temperatures, and distribution functions, including massive neutrinos, may be represented as a single effective HDM species. Implementing this method in the FlowsForTheMasses non-linear perturbation theory for free-streaming particles, we study non-standard HDM models that contain thermal QCD axions or generic bosons in addition to standard neutrinos, as well as non-standard neutrino models wherein either the distribution function of the neutrinos or their temperature is changed. Along the way, we substantially improve the accuracy of this perturbation theory at low masses, bringing it into agreement with the high-resolution TianNu neutrino N-body simulation to about 2% at k = 0.1 h/Mpc and to within 21% up to k = 1 h/Mpc. We accurately reproduce the results of simulations including axions and neutrinos of multiple masses. Studying the differences between the normal, inverted, and degenerate neutrino mass orderings on their non-linear power, we quantify the error in the common approximation of degenerate masses. We release our code publicly at http://github.com/upadhye/FlowsForTheMassesII .
format Preprint
id arxiv_https___arxiv_org_abs_2410_05815
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Everything hot everywhere all at once: Neutrinos and hot dark matter as a single effective species
Upadhye, Amol
Mosbech, Markus R.
Pierobon, Giovanni
Wong, Yvonne Y. Y.
Cosmology and Nongalactic Astrophysics
High Energy Physics - Phenomenology
Observational cosmology is rapidly closing in on a measurement of the sum M_nu of neutrino masses, at least in the simplest cosmologies, while opening the door to probes of non-standard hot dark matter (HDM) models. By extending the method of effective distributions, we show that any collection of HDM species, with arbitrary masses, temperatures, and distribution functions, including massive neutrinos, may be represented as a single effective HDM species. Implementing this method in the FlowsForTheMasses non-linear perturbation theory for free-streaming particles, we study non-standard HDM models that contain thermal QCD axions or generic bosons in addition to standard neutrinos, as well as non-standard neutrino models wherein either the distribution function of the neutrinos or their temperature is changed. Along the way, we substantially improve the accuracy of this perturbation theory at low masses, bringing it into agreement with the high-resolution TianNu neutrino N-body simulation to about 2% at k = 0.1 h/Mpc and to within 21% up to k = 1 h/Mpc. We accurately reproduce the results of simulations including axions and neutrinos of multiple masses. Studying the differences between the normal, inverted, and degenerate neutrino mass orderings on their non-linear power, we quantify the error in the common approximation of degenerate masses. We release our code publicly at http://github.com/upadhye/FlowsForTheMassesII .
title Everything hot everywhere all at once: Neutrinos and hot dark matter as a single effective species
topic Cosmology and Nongalactic Astrophysics
High Energy Physics - Phenomenology
url https://arxiv.org/abs/2410.05815