In her lecture, Professor Freese distinguishes between ordinary neutrons and sterile neutrinos. Sterile neutrinos are an exotic type of neutrino that have been theorized (outside the Standard Model) to interact only through gravity. There's increasing optimism that sterile neutrinos are a viable candidate for dark matter and directly detectable. Moreover, on one of her slides, she lists primordial black holes (black holes formed shortly after the Big Bang) as a candidate for dark matter. In subsequent work, she and a collaborator investigate whether primordial black holes of varying masses could constitute all of the observed dark matter and they show that it's indeed plausible.