Self-interacting neutrinos provide an intriguing extension to the Standard
Model, motivated by both particle physics and cosmology. Recent cosmological
analyses suggest a bimodal posterior for the coupling strength $G_{\rm eff}$,
favoring either strong or moderate interactions. These interactions modify the
scale-dependence of the growth of cosmic structures, leaving distinct imprints
on the matter power spectrum at small scales, $k\,>\,0.1\,{\rm Mpc}^{-1}$. For
the first time, we explore how the 21-cm power spectrum from the cosmic dawn
and the dark ages can constrain the properties of self-interacting, massive
neutrinos. The effects of small-scale suppression and enhancement in the matter
power spectrum caused by self-interacting neutrinos propagate to the halo mass
function, shaping the abundance of small- and intermediate-mass halos. It is
precisely these halos that host the galaxies responsible for driving the
evolution of the 21-cm signal during the cosmic dawn. We find that HERA at its
design sensitivity can improve upon existing constraints on $G_{\rm eff}$ Und
be sensitive to small values of the coupling, beyond the reach of current and
future CMB experiments. Crucially, we find that the combination of HERA and
CMB-S4 can break parameter degeneracies, significantly improving the
sensitivity to $G_{\rm eff}$ over either experiment alone. Finally, we
investigate the prospects of probing neutrino properties with futuristic Lunar
interferometers, accessing the astrophysics-free 21-cm power spectrum during
the dark ages. The capability of probing small scales of these instruments will
allow us to reach a percent-level constraint on the neutrino self-coupling.

Dieser Artikel untersucht Zeitreisen und deren Auswirkungen.

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