Seminars : Documents

Probing Early universe with Gravitational waves at nano-frequencies
Rome Samanta (CEICO, Institute of Physics, Czech Academy of Sciences, Prague.)

The discovery of Gravitational Waves (GWs) by LIGO and Virgo collaboration has unequivocally opened up a new cosmic frontier for the multi-frequency study of stochastic GW background (SGWB). There are several sources in the Early Universe (EU) that can produce detectable SGWB. Interestingly, recently the NANOGrav pulsar timing array (PTA) collaboration have reported strong evidence for a stochastic common-spectrum process over independent red-noises across 45 pulsars at a frequency f~1/yr. If this is interpreted as GWs, several interesting mechanisms such as models of inflation, primordial black hole dark matter, and baryogenesis can be probed. In this talk, I will briefly summarise some of the mechanisms/sources that can produce GW at nano-frequencies and therefore testable by the PTAs. I will particularly give emphasis on the models of baryogenesis and discuss how PTAs serve as novel probes of baryogenesis-one of the unresolved cosmological puzzles to date.