Sterile Neutrino Decays During the Weak Decoupling Era

In the early universe, the weak decoupling era – when the active neutrinos begin to fall out of thermal and chemical equilibrium – provides a unique opportunity to explore neutrino physics and the connections between Beyond Standard Model and neutrino physics. We explore the decay of sterile neutrinos during the weak decoupling era into Standard Model particles, including neutrinos. The result is distorted active neutrino spectra. This talk will explore the out-of-equilibrium production of these spectra, the altered time-temperature relationship in the early universe, and the impacts on cosmological observables.