GRAV In the literature: partially resolved

How does Hawking emission change the analog horizon that produces it?

In plain words

A real black hole should shrink as it radiates; in a condensate the emitted sound should likewise change the flow that makes the horizon. Theory now predicts how much the flow is changed, but no experiment has measured the change.

Precise statement

For a quasi-1D BEC sonic black hole, the back-reaction of the Hawking flux on the flow, to first order in the quantum depletion 1/(n_1D $\xi$) (n_1D the linear density, xi the healing length), has been computed as a stationary shift of the density, velocity and Mach-number profiles. Determine whether the surface gravity $\kappa$ also drifts in time (sign and rate of $\mathrm{d}\kappa/\mathrm{d}t$, and whether the evolution follows an evaporation law analogous to $\mathrm{d}M/\mathrm{d}t$ proportional to $-T_H^2$), and measure the predicted stationary or time-dependent profile change. An answer is a measured profile change that agrees with the computed one after three-body loss, heating and stimulated emission are subtracted.

What would settle it

A measurement of the density, velocity or Mach-number profile change in a stationary BEC analog that matches the computed back-reaction after atom loss and heating are subtracted.

Status in the literature

Unverified note

Back-reaction equations were derived (Liberati, Tricella, Trombettoni 2020; Balbinot, Fabbri, Ciliberto, Pavloff 2025), and Ciliberto et al. (PRA 112, 063323, 2025) computed a stationary Mach-number shift; no measurement has isolated the effect as of 2026.

See also