Does running inflation backward change how rare black holes form?

Running the equations of inflationary quantum diffusion backward in time — from the end of inflation toward its beginning — gives a subtly different picture than the standard forward approach. In a bounded flat potential, large fluctuations develop exponential tails that decay twice as fast as conventional calculations predict. Since primordial black holes form precisely from those rare large fluctuations, this time-reversal perspective could meaningfully shift estimates of how many formed in the early universe.