Primordial Black Holes from Domain Wall Density Fluctuations: Bridging Gravitational Wave Observations Across Two Frequency Bands

We propose a novel mechanism for the formation of primordial black holes by demonstrating that the delayed production of isocurvature perturbations resulting from Poisson fluctuations within the domain wall network can lead to collapse and the formation of primordial black holes during the horizon crossing of domain walls. Our findings establish a statistical relationship between the number of domains and the power spectrum of the perturbations. This relationship can be employed to constrain the symmetry of the model in light of the potential overabundance of primordial black holes. Furthermore, by incorporating the effects of accretion, we demonstrate that the annihilation of the domain wall network at the QCD scale may provide a plausible common origin for gravitational wave observations across two distinct frequency bands.