Cosmological Implications of a Neutrino Mass Detection

Abstract

The next generation of cosmological surveys are expected to measure a non-zero sum of neutrino masses, even down to the minimum value of 58 meV inferred from neutrino flavor oscillation. The implications of such a measurement for the physics of neutrinos have been well documented; in contrast, the cosmological implications of such a measurement have received less attention. In this paper, we explore the impact of a neutrino mass detection consistent with m ν = 58 meV for our understanding of the history and contents of the universe. We focus primarily on three key areas: the thermal history of the universe, clustering of matter on diverse scales, and the application to dark matter and dark sectors. First we show that a detection of non-zero neutrino mass would provide a unique connection between the cosmic neutrino background, which is detected gravitationally, and neutrinos measured on Earth. We then discuss how the consistency of a detection between multiple probes will impact our knowledge of structure formation. Finally, we show how these measurements can be interpreted as sub-percent level tests of dark sector physics.

The Physics of Light Relics

“…In this regime, the shape of the suppression of the matter power spectrum (see Figure 3) is difficult or impossible to resolve, implying that observations are only sensitive to the amplitude of the suppression. These low-mass LiMRs therefore have observational signatures that can be well captured in terms of Δ𝑁 eff and 𝑚 𝜈 [91]. Similarly, models in which a fraction of the dark matter acquires a large velocity after recombination (e.g.…”

“…via DM-neutrino scattering [92]) will lead to a suppression of clustering in a manner similar to that described above. Despite the different physical mechanism, the observable consequences for cosmology are also similar to a change to 𝑚 𝜈 [91]. Cosmological measurements of both 𝑁 eff and 𝑚 𝜈 provide useful insights for dark sector physics.…”

The resilience of the Etherington-Hubble relation

“…For instance, as robustly indicated by oscillation experiments (de Salas et al 2021;De Salas et al 2018), neutrinos should be regarded as massive particles, and cosmology provides a powerful (albeit indirect) means to constrain their mass (De Salas et al 2018;Hagstotz et al 2020;Vagnozzi 2019;Vagnozzi et al 2018aVagnozzi et al ,b, 2017Giusarma et al 2016;Bond et al 1980;Capozzi et al 2021;Di Valentino et al 2021b;Xu et al 2021;Green & Meyers 2021). The strong correlation between the expansion rate and the total neutrino mass can alter the final constraint on 𝐻 0 .…”

The Benefits of CMB Delensing

“…structure at late times, including neutrino mass [9][10][11][12][13] and dark energy [14]. The value of CMB lensing maps are enhanced by the opportunities presented by cross-correlations with large scale galaxy surveys [15][16][17][18][19].…”