Could We Observe an Exploding Black Hole in the Near Future?

TL;DR

The paper addresses the challenge of observing exploding primordial black holes (PBHs) under conventional Schwarzschild evolution, which is tightly constrained by indirect limits on Hawking radiation. It introduces a dark U(1) sector with a heavy dark electron, producing quasi-extremal PBHs whose Hawking emission is suppressed for long periods before a dark Schwinger discharge triggers a Schwarzschild-like explosion. Depending on the dark-sector parameters, the local explosion rate can be significantly enhanced, and a log-normal PBH mass distribution can yield non-negligible detection probabilities for HAWC and LHAASO within a decade, while remaining compatible with CMB and EGRB constraints. This mechanism offers a plausible path to near-term observation of PBH explosions, with broader implications for testing Hawking radiation and probing the particle content of nature, and could extend to other beyond-Standard-Model scenarios.

Abstract

Observation of an exploding black hole would provide the first direct evidence of primordial black holes, the first direct evidence of Hawking radiation, and definitive information on the particles present in nature. However, indirect constraints suggest that direct observation of an exploding Schwarzschild black hole is implausible. We introduce a dark-QED toy model consisting of a dark photon and a heavy dark electron. In this scenario a population of light primordial black holes charged under the dark $u(1)$ symmetry can become quasi-extremal, so they survive much longer than if they were uncharged, before discharging and exhibiting a Schwarzschild-like final explosion. We show that the answer is "yes", in this scenario the probability of observing an exploding black hole over the next $10$ years could potentially be over $90\%$.

Figures (3)

• Figure 1: PBH mass (blue), charge (red) and temperature (orange) evolution for $m_D=10^{10}\,$GeV and $e_D=10^{-3} e_{\rm SM}$. We also show $\tau_{\rm Schw}$ (the lifetime of a Schwarzschild PBH of the same initial mass), $t_{\rm CMB}$ (the time of recombination) and $t_{\rm universe}$ (the age of the universe today).
• Figure 2: Indirect bounds on $f_{\rm PBH}$ from BBN (red), CMB (blue) and the EGRB (grey) during the initial evaporation phase and from both the CMB and EGRB (black) during the final explosion for three different benchmark points (A, B and C).
• Figure 3: Maximum burst rates consistent with the CMB and EGRB constraints for a log-normal mass distribution of PBHs with $\sigma_M = 0.3$ and $Q_D^{*i}=0.01$, along with the corresponding probability of an observation at HAWC (yellow) and LHAASO (magenta) with 10 years of data. The $y$-axis shows both the discharge mass (left) and the approximate critical mass (right). In the upper right corner perturbativity does not apply while on the far left the condition $Q_D e_D/r_+ > m_D$ is not satisfied. We also indicate the positions of the benchmark points A, B and C.