LVK constraints on PBHs from stochastic gravitational wave background searches

Primordial black holes (PBHs) may have left an imprint in the form of a stochastic gravitational wave background (SGWB) throughout their evolution in the history of the Universe. This review highlights two types of SGWB: those generated by scalar curvature perturbations associated with PBH formation in the early Universe and those composed of ensembles of GWs emitted by PBH binaries. After describing detection methods and a brief introduction on Bayesian inference, we discuss current constraints imposed by LIGO-Virgo-KAGRA (LVK) observations through the non-detection of the SGWBs and discuss their physical implications.