{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"b5f46790e3cb373e65e4bc48de68480bfe7021d6da27963dfb57de634d1287ba","created":"2026-10-03T07:18:04Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"49816b0edf34e9c3c7d3fc888140416bea450c00c08aeddbbf4657b127b41548","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"grav.analog-hawking.analog-backreaction","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"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.","posed_since":"","precise":"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.","problem_ref":null,"references":"","settled_by":"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_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.","title":"How does Hawking emission change the analog horizon that produces 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