Speaker
Description
We propose a new probe of primordial non-Gaussianities through
the observational window of gravitational waves (GW) being induced by
ultra-light ($M_{\text{PBH}}< 10^{9}\rm{g}$) primordial black holes
(PBHs). An existence of primordial non-Gaussianity can leave imprints on
the clustering properties of PBHs and the spectral shape of the induced
GW signal. Focusing on local-type non-Gaussianities, we find a
distinctive double-peaked GW energy spectrum which, depending on the PBH
mass $M$ and the initial PBH abundance at formation time, i.e.
$\Omega_\mathrm{PBH,f}$, can lie within the frequency bands of
forthcoming GW detectors, including LISA, ET, SKA and BBO, hence
rendering this signal promisingly detectable by GW experiments and
promoting it as a novel portal probing non-Gaussianities. Moreover, by
accounting on BBN bounds on the non-Gaussian GW amplitude we set
model-independent constraints on the effective $\tau_\mathrm{NL}$,
denoted as $\bar{\tau}_\mathrm{NL}(k)$, on scales
$k>10^5\mathrm{Mpc}^{-1}$, which read as $\bar{\tau}_\mathrm{NL}(k)
\mathcal{P}_{\cal R}(k) < 2\times 10^{-20} \Omega^{-17/9}_\mathrm{PBH,f}
\left( \frac{M_{\rm PBH}}{10^4\mathrm{g}} \right)^{-17/9}$, where
$\mathcal{P}_{\cal R}(k)$ is the primordial curvature power spectrum.
