Constraints on the inflationary vacuum and reheating era from NANOGrav
The episode discusses a paper constraining inflationary vacuum and reheating era from NANOGrav data, which looks for a stochastic gravitational wave background signal. The authors use Markov chain Monte Carlo analyses to suggest a radiation-like reheating scenario but find tension with Big Bang Nucleosynthesis constraints. They propose an alpha-vacuum model with frequency dependence as a solution.