GW190521: Search for echoes due to stimulated Hawking radiation from black holes
Bibliographic record
Abstract
Being arguably the most massive binary black hole merger event observed to date, GW190521 deserves special attention. The exceptionally loud ringdown of this merger makes it an ideal candidate to search for gravitational wave echoes, a proposed smoking gun for the quantum structure of black hole horizons. We perform a multipronged search for echoes via two well-established and independent pipelines; a template-based search for stimulated emission of Hawking radiation, or Boltzmann echoes, and the model-agnostic coherent WaveBurst (cwb) search. Stimulated Hawking radiation from the merger is proposed to lead to postmerger echoes at horizon mode frequency of $\ensuremath{\sim}50\text{ }\text{ }\mathrm{Hz}$ (for quadrupolar gravitational radiation), repeating at intervals of $\ensuremath{\sim}1$ second, due to partial reflection off Planckian quantum structure of the horizon. An analysis using dynamic nested sampling yields a Bayesian evidence of ${8}_{\ensuremath{-}2}^{+4}$ (90% confidence level) for this signal following GW190521, carrying an excess of ${6}_{\ensuremath{-}5}^{+10}%$ in gravitational wave energy, relative to the main event (consistent with the predicted amplitude of Boltzmann echoes). The ``look-elsewhere'' effect is estimated by using general relativity (plus Boltzmann echoes) injections in real data, before and after the event, giving a false (true) positive detection probability for higher Bayes factors of ${1.5}_{\ensuremath{-}0.9}^{+1.2}%$ ($35\ifmmode\pm\else\textpm\fi{}7%$). Similarly, the reconstructed waveform of the first echo in cwb carries an energy excess of ${13}_{\ensuremath{-}7}^{+16}%$. While the current evidence for stimulated Hawking radiation does not reach the gold standard of $5\ensuremath{\sigma}$ (or p-value $<3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$), our findings are in line with predictions for stimulated Hawking radiation at current detector sensitivities. The next generation of gravitational wave observatories can thus draw a definitive conclusion on the quantum nature of black hole horizons.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".