A black hole is not an eternal vacuum cleaner. It slowly loses mass by emitting particles, much like a heated stone cooling as it radiates heat. This process, discovered by Stephen Hawking, is barely noticeable for large holes, but for tiny ones, with masses comparable to a mountain, it becomes a violent evaporation. If such 'primordial' black holes were born in the early universe, they would be reaching their final stages today, and could be part of dark matter.
In the new calculation, physicists took a black hole in empty space and tracked how it spawns electrons and positrons. Previously, this process was described semiclassically: particles appeared almost on schedule, but with a slight random glitch — the 'stochastic charge.' Now the authors derived the same effect from first principles of quantum electrodynamics on the curved spacetime of Schwarzschild. It turns out that quantum corrections almost completely suppress this glitch: for masses between 22 and 170 million tons, the deviation from a steady stream is less than two percent.
This result narrows the search corridor: if the radiation turns out to be slightly smoother than expected, that's not a detector artifact: it's the very nature of the quantum world. The black hole ceases to be just a 'stone' shedding sparks; it becomes a system where each particle obeys a delicate interplay of charges and fields.
A primordial black hole with a mass of 10¹⁶ grams (ten billion tons) is about the size of a proton, roughly 10⁻¹³ centimeters, and its surface temperature exceeds 10¹¹ kelvin, thousands of times hotter than the core of the Sun.
In David Brin's novel 'Startide Rising,' intelligent beings use microscopic black holes as a power source, balancing on the edge of their complete evaporation.