Hiding neutrino mass in modified gravity cosmologies

TL;DR

This paper investigates how modifications in gravity theories, specifically Horndeski models, can mimic or hide the effects of neutrino mass in cosmological observations, affecting neutrino mass measurements.

Contribution

It identifies a dominant parameter in Horndeski theories that cancels neutrino mass effects, and assesses how this impacts neutrino mass constraints from cosmological data.

Findings

A single effective parameter correlates strongly with neutrino mass.

Certain parameter values can cancel neutrino mass effects at specific redshifts.

Gravity modifications can significantly influence neutrino mass constraints.

Abstract

Cosmological observables show a dependence with the neutrino mass, which is partially degenerate with parameters of extended models of gravity. We study and explore this degeneracy in Horndeski generalized scalar-tensor theories of gravity. Using forecasted cosmic microwave background and galaxy power spectrum datasets, we find that a single parameter in the linear regime of the effective theory dominates the correlation with the total neutrino mass. For any given mass, a particular value of this parameter approximately cancels the power suppression due to the neutrino mass at a given redshift. The extent of the cancellation of this degeneracy depends on the cosmological large-scale structure data used at different redshifts. We constrain the parameters and functions of the effective gravity theory and determine the influence of gravity on the determination of the neutrino mass from present and future surveys.