Speaker
Description
In this talk, I will explore the potential of multi-band gravitational wave (GW) observations to constrain uncertainties in the Hubble parameter ($H_0$), using primordial black holes (PBHs) as astrophysical sources. I will present a framework that combines scalar-induced and merger-induced GW signals and discuss forecasts for joint observations with the Square Kilometre Array (SKA) and the Einstein Telescope (ET), enabling a multi-band analysis. I will then show how statistical forecasts of PBH parameters, $M_{\rm PBH}$ and $f_{\rm PBH}$, based on signal-to-noise ratio (SNR) and Fisher matrix techniques, allow us to identify the accessible parameter space and propagate uncertainties to $H_0$. For $\delta \theta_i/\theta_i \leq 0.1$, with $\theta_i \equiv M_{\rm PBH}(f_{\rm PBH})$, we obtain $\delta H_0 \leq 2~{\rm km,s^{-1},Mpc^{-1}}$, improving to $\delta H_0 \leq \mathcal{O}(0.1)~{\rm km,s^{-1},Mpc^{-1}}$ for $\delta \theta_i/\theta_i \leq 0.01$. Finally, I will highlight that these results are largely insensitive to the fiducial value of $H_0$, with only moderate dependence on the PBH collapse efficiency, demonstrating that multi-band GW observations provide a complementary, cosmic distance ladder-independent probe of the Hubble parameter.
Reference: e-Print: 2604.22731
