In recent years, different Pulsar Timing Arrays (PTA) observatories reported strong evidence for a common-spectrum process in their searches, and the data released last year strengthened the interpretation that the signal is caused by a stochastic gravitational wave (GW) background. A common interpretation of the GW signal is that it originates from Supermassive Black Hole Binaries. In this talk, I will briefly review the evidence for the GWs and discuss an alternative interpretation that we recently proposed, based on new physics that is closely connected to QCD, and that fits the data as well as the more vanilla explanation.
Organized by: Paulo Brás, Paulo Silva, Jaime Silva