The 'Poltergeist' gravitational wave signal from black holes was wildly overestimated

When tiny primordial black holes evaporate and reheat the early universe, they were predicted to produce a strong 'Poltergeist' gravitational wave burst. Including the inevitable mass spread from gravitational collapse — a consequence built into General Relativity itself — smooths the transition enough to kill that signal almost entirely, leaving only a much quieter background. The result reopens a swath of parameter space for ultra-light primordial black holes that observers thought they had already ruled out.