Primordial extremal black holes as dark matter

We show that primordial (nearly) extremal black holes with a wide range of masses from the Planck scale to around 109 g could be cosmologically stable and provide a viable explanation for dark matter, given a dark electromagnetism and a heavy dark electron. Hawking radiation and Schwinger discharge processes are suppressed by near extremality and the heaviness of the dark electron, respectively. The merger events of binary systems with opposite charges generate nonextremal black holes, whose subsequent Hawking evaporation produces transient neutrino and gamma ray signals to be observed at telescopes like IceCube and HAWC. The relationship between the near-extremal black hole and dark electron masses could also shed light on the weak gravity conjecture.