Tiny Black Holes Don’t Warp the Cosmos ⚡ экспресс
The problem of back-reaction of enhanced short-wavelength perturbations on large-scale modes is studied in single-field inflationary scenarios for primordial black hole generation. Such scenarios require a sharp increase in the curvature power spectrum on scales much smaller than those accessible in cosmic microwave background observations, and are typically realized through a brief phase of ultra-slow roll, which violates standard dynamics. Using the 'separate universes' formalism and its generalization with multi-point propagators, it is shown that the influence at the one-loop level reduces to two effects: nonlinear evolution of perturbations on superhorizon scales or one-loop corrections to initial conditions. Assuming adiabaticity and scale separation, the unobservability of such back-reaction is established, and consequently, the decoupling of large-scale and short-wavelength dynamics. The results guarantee that predictions for large-scale structure remain unspoiled in single-field models; the limits of applicability are discussed separately.
Right after the Big Bang, the Universe expanded incredibly fast — this phase was called inflation. In some microscopic regions, matter randomly clumped so much that it collapsed into primordial black holes. They are tiny — the size of a proton, yet as massive as an iceberg.
Scientists were tormented by the question: wouldn’t these turbulent small-scale processes spoil the delicate picture of large-scale waves we observe in the cosmic microwave background? Alan Guth soothed: the basses and flutes in the cosmic symphony play at different frequencies and don’t interfere with each other. New calculations proved that any back-reaction is a thousand times weaker than the sensitivity threshold of our instruments. The melody of the cosmos remains pure.
Thus primordial black holes earned the right to be considered part of dark matter — the invisible substance that holds galaxies together. The irony is that, according to Stephen Hawking’s calculations, ordinary black holes evaporate, while these long-lived ones will exist forever.
🎯 A black hole the size of a proton has the mass of an iceberg.