Speaker
Description
Cosmic strings are a well-motivated source of stochastic gravitational-wave backgrounds (SGWBs), but current pulsar timing array (PTA) data are often interpreted as favoring the supermassive black hole binary scenario over the standard Nambu–Goto string SGWB template. In this talk, I will show that this conclusion can change once cosmic strings are allowed to explore extra dimensions. The key effect is that exact cusps are no longer generic and are instead replaced by near-cusp events. The modified beaming and phase space of these events reshape the PTA-band spectrum rather than simply rescaling its amplitude. I will present a phenomenological model of this effect and its preliminary confrontation with NANOGrav data through Bayesian inference. The results suggest that extra-dimensional dynamics may reopen cosmic strings as a viable interpretation of the nanohertz SGWB.