The Magnetic Origin of Primordial Black Holes: A Viable Dark Matter Scenario

Primordial Black Holes (PBHs) are compelling candidates for explaining the present-day relic abundance of cold dark matter (CDM), yet their formation typically requires finely tuned early-universe dynamics. In this work, we propose a novel PBH formation mechanism within a well-established magnetogenesis framework. This scenario simultaneously accounts for the large-scale magnetic fields observed today and generates an enhanced curvature power spectrum at intermediate scales, leading to PBH formation with masses that can survive until the present epoch. We identify a narrow reheating temperature range, ${10}^5\mathrm{G}\mathrm{e}\mathrm{V}\le T_{re}\le 3\times {10}^5\mathrm{G}\mathrm{e}\mathrm{V}$, within which the resulting PBHs can constitute the entirety of the observed CDM abundance. Furthermore, our model predicts a stochastic gravitational wave (GW) background as a byproduct of the PBH formation process. Remarkably, the predicted GW signal lies within the sensitivity reach of upcoming space-based interferometers, such as the LISA, DECIGO, or SKA mission, offering a direct observational probe of this PBH generation mechanism.