Measuring neutrino mass in light of ACT DR6 and DESI DR2

TL;DR

This paper uses recent high-precision cosmological data from ACT and DESI to update constraints on neutrino mass across various dark energy models, highlighting the impact of dark energy behavior on these limits.

Contribution

It provides the first comprehensive analysis of neutrino mass constraints incorporating ACT DR6 and DESI DR2 data across multiple dark energy models, emphasizing model-dependent effects.

Findings

Early-time quintessence models yield tighter neutrino mass constraints.

Allowing early-time phantom behavior results in looser bounds.

Inverted hierarchy consistently yields weaker constraints than degenerate hierarchy.

Abstract

The recent release of high-precision cosmological data, particularly the small-scale cosmic microwave background (CMB) measurements from ACT and baryon acoustic oscillation (BAO) data from DESI, has opened a new landscape for probing the neutrino mass. In this work, we present updated constraints on the total neutrino mass, $\sum m_\nu$, and its hierarchy within the $\Lambda$CDM, $w$CDM, holographic dark energy (HDE), and $w_0w_a$CDM models, using the latest ACT DR6, DESI DR2, and DESY5 datasets. We find that the upper limits on $\sum m_\nu$ are critically governed by the evolutionary behavior of the dark energy equation of state. Specifically, models exhibiting early-time quintessence features (e.g., HDE) yield the most stringent constraints, whereas those allowing for early-time phantom behavior (e.g., $w_0w_a$CDM) result in significantly looser bounds. Despite these model-dependent variations, we observe a robust hierarchy dependence across all scenarios, where the inverted hierarchy consistently yields weaker constraints and the degenerate hierarchy consistently yields tightest constraints. Our analysis demonstrates that the improved small-scale CMB information from ACT, combined with high-precision BAO data, systematically tightens the limits on $\sum m_\nu$, providing a crucial benchmark for future neutrino mass measurement.