Title：Theoretical milestones and recent progress on the nanohertz gravitational wave background
Time：2023/05/08 (Mon.) 12:30
Place：R517, New Physics Building, NTU

Abstract：
Nanohertz gravitational waves (GW) superpose into a galactic stochastic gravitational wave background that spatially correlates astronomical observations. We briefly look back at the theoretical milestones of the field -- from the first proposals to utilize an array of millisecond pulsars, to the Hellings-Downs curve, and the common spectrum process viewed today by the leading pulsar timing arrays (PTA) -- and then discuss recent progress. We put emphasis on recent work that advocated the use of the correlations for the unequivocal detection of the GW background, and the power spectrum approach that is a calculational bridge between all GW polarizations and the higher moments of the correlation. To end, we draw future directions in PTA cosmology.