Do cosmological tensions indicate new neutrino physics?

Neutrino oscillation experiments have recognized that neutrinos have a mass that can significantly affect cosmological observables. Fixing the sum of the neutrino masses to 0.06 eV is based on the minimum value allowed by oscillation experiments. By considering different distributions of the sum of the neutrino masses as well as allowing it to be a free parameter, I will compare the Standard Cosmological Model case and explore the actual cosmological bounds on sterile neutrino masses in the light of the Hubble and S8 tensions. Connected to these tensions and the unknown early history of the Universe I will present a "Low reheating Temperature" Scenario that remains consistent with primordial nucleosynthesis and accommodates several new physics scenarios that would normally be constrained by high-temperature reheating models. The expansion history and thermal physical process that happened in the early Universe before big bang nucleosynthesis remains relatively unconstrained by observations. In this talk, I will introduce the production of keV-scale sterile neutrinos in such scenarios and their resulting constraints from cosmological observations. In addition, I will show how this mechanism of sterile neutrinos with large mixing may provide a solution to the Hubble tension and that these keV-scale sterile neutrinos are one of the best probes of the untested pre-BBN era in the early Universe and could be seen in upcoming laboratory experiments.