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 an unprecedented multi-pronged 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 expected to lead to post-merger echoes at horizon mode frequency of $\sim50$ Hz (for quadrupolar gravitational radiation), repeating at intervals of $\sim1$ second, due to partial reflection off Planckian quantum structure of the horizon. A careful analysis using dynamic nested sampling yields a Bayesian evidence of $8^{+4}_{-2}$ (90\% confidence level) for this signal following GW190521, carrying an excess of $6^{+10}_{-5}\%$ 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, around the event, giving a false (true) positive detection probability for higher Bayes factors of $1.5^{+1.2}_{-0.9}\%$ ($35\pm7\%$). Similarly, the reconstructed waveform of the first echo in cWB carries an energy excess of $13^{+16}_{-7}\%$. While the current evidence for stimulated Hawking radiation does not reach the gold standard of $5σ$ (or p-value $<3\times10^{-7}$), our findings are in line with expectations 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.
Symplectic circuits, entanglement, and stimulated Hawking radiation in analog gravity
我们引入了一套方便的分析工具（高斯形式）和图表（辛电路）来分析模拟引力中的多模散射事件，如黑洞和白洞模拟事件视界对创建a lá Hawking。该图被证明是有价值的ansatzes的散射动力学，特别是在设置直接的分析结果是不直接的，而必须依赖于数值模拟。我们使用这些工具来研究单视界和多视界场景中的纠缠产生，特别是当霍金过程被经典（例如，热噪声）和非经典（例如，单模压缩真空）输入态--例如，表明初始压缩可以增强纠缠的产生，并克服初始热涨落对输出纠缠的有害影响。为了进一步接触实际问题，我们研究衰减如何降低霍金对之间的量子相关性。我们所采用的技术一般适用于（高斯）玻色子量子系统的模拟重力设置，如光学模拟和玻色-爱因斯坦凝聚体中产生的模拟视界，并且应该在这些领域中具有很大的实用性。我们显示这些技术的适用性，把他们在行动中的光学系统包含一对白色-黑洞模拟，扩展我们以前的分析[物理评论快报。128，091301（2022）]。
Non-linear Processes and Stimulated Hawking Radiation in Hydrodynamics for Decelerating Subcritical Free Surface Flows with a Subluminal Dispersion Relation
Quasinormal Modes and Hawking Radiation of Black Holes with Primary Scalar Hair
Research Centre for Theoretical Physics and Astrophysics, Institute of Physics, Silesian University in Opava（奥帕瓦西里西亚大学物理研究所理论物理与天体物理研究中心）；Institute of Cosmology, Department of Physics and Astronomy, Tufts University（塔夫茨大学物理与天文学系宇宙学研究所）；Institute of Physics in Opava, Silesian University in Opava（奥帕瓦西里西亚大学奥帕瓦物理研究所）
A scenario for black hole evaporation on a quantum geometry
我们将最近发现的真空球对称时空的圈量子引力的量子约束的精确解的元素，由于Ashtekar和Bojowald的黑洞蒸发的范例。解的对称面面积的量子化意味着，可以装进黑洞内部的好片的数量是有限的。叶理最终穿过经典理论中的奇点所在的区域，所有由于霍金辐射而落入黑洞的粒子最终以白洞的形式出现。这产生了Arkani-Hamed { \em et al.}主张的一种方案的变体。在量子时空中自然产生的视界波动允许辐射在蒸发过程中出现，这是由于受激发射允许蒸发进行到超过Page时间而没有达到最大纠缠极限，直到白洞形成。在这种情况下，不会出现防火墙或残留物。
