Primordial extremal black holes as dark matter

Abstract

We show that primordial (nearly) extremal black holes with a wide range of masses from the Planck scale to around 10 9 g could be cosmologically stable and explain dark matter, given a dark electromagnetism and a heavy dark electron. For individual black holes, Hawking radiation and Schwinger discharge processes are suppressed by near-extremality and the heaviness of the dark electron, respectively. In contrast, the merger events of binary systems provide an opportunity to directly observe Hawking radiation. Because the merger products are not extremal, they rapidly evaporate and produce transient high-energy neutrino and gamma ray signals that can 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.

Phenomenology of magnetic black holes with electroweak-symmetric coronas

“…PMBHs can be captured by the Sun, drift into the core of the Sun, and merge to produce non-extremal RN BHs that Hawking radiate energetic neutrinos. This high energy particle signal from merging extremal BHs was pointed out in a different context in [21]. In addition, PMBHs that are captured but have not yet annihilated can mediate BNV processes, which could also be detected by the energetic particles they emit.…”

“…For instance, if GUT monopoles exist, the EWS-corona BH may be Schwinger discharged by emitting GUT monopoles. The lower bound on Q is (omitting a logarithmic factor, see [21,26,27])…”

“…We have not discussed how PMBHs form, instead focusing on the phenomenology if they are present. One example of a formation mechanism is that they may start as ordinary primordial BHs, then absorb on average N randomly charged monopoles leaving them with a typical charge ∼ √ N , then Hawking radiate until they approach near extremality [20,21]. In such a scenario, bounds from the effects of their evaporation on Big Bang nucleosynthesis, the cosmic microwave background, and gamma rays could set additional constraints [101].…”

“…Leaving aside the early universe production of primordial MeBHs (PMBHs) (see refs. [20,21] for early universe production of primordial eBHs and refs. [22,23] for recent reviews of primordial uncharged BH production), the immediate questions are how abundant MeBHs can be in the current Universe and how to detect them, which will be the main topics of this paper.…”

“…For instance, when we consider the capture rate of MeBHs by astrophysical objects, both the finite size and large magnetic charge of MeBHs will be taken into consideration. Furthermore, given the BH in the core, Hawking radiation also plays a role when either two MeBHs with opposite charges merge or one MeBH absorbs ordinary matter to become a non-extremal BH [21]. This Hawking radiation provides a unique signal not found in ordinary monopoles.…”