Cosmological Constraints on Dark Neutrino Towers

TL;DR

This paper investigates how dark neutrino KK towers in a dark dimension influence cosmological parameters, deriving constraints on active-sterile neutrino conversion rates and addressing claims about extra dimensions.

Contribution

It provides new cosmological bounds on dark neutrino KK towers and counters recent claims about the implications of extra dimensions on $ _{ m eff}$.

Findings

Constraints on active-sterile neutrino conversion rates derived from cosmological data.

Weak decay channels of neutrino KK towers can significantly impact cosmology.

Counterarguments to claims that $ _{ m eff}$ bounds exclude micron-sized extra dimensions.

Abstract

We reexamine a dynamical dark matter model with Kaluza-Klein (KK) towers of gravitons and neutrinos fitting together in the dark dimension. We show that even though gravitational decays of neutrino KK towers have little impact in cosmology the weak decay channel could have significant cosmological effects. Taking conservative upper bounds on the dark matter decay rate into two photons before recombination and on the number of effective extra neutrino species $\Delta N_{\rm eff}$ we derive constraints on the conversion rate from active to sterile species despite the dependence of the mixing angle on the KK mode mass. We also provide counterarguments to a recent claim suggesting that the bounds on $\Delta N_{\rm eff}$ rule out micron-sized extra dimensions.