BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Gravity and Cosmology -my personal recollections and perspectives- DTSTART;VALUE=DATE-TIME:20260522T080000Z DTEND;VALUE=DATE-TIME:20260522T090000Z DTSTAMP;VALUE=DATE-TIME:20260530T132724Z UID:indico-contribution-556-2454@indico.itp.ac.cn DESCRIPTION:Speakers: Misao Sasaki (APCTP)\nI will talk about various topi cs in gravity and cosmology which I have been studying through my academic life\, and discuss my personal perspectives.\n\nhttps://indico.itp.ac.cn/ event/419/contributions/2454/ LOCATION:Small Lecture Hall\, Chongqing University Library (图书馆小 报告厅) 1F-9 URL:https://indico.itp.ac.cn/event/419/contributions/2454/ END:VEVENT BEGIN:VEVENT SUMMARY:Quantum Treatment of Black Hole Superradiance DTSTART;VALUE=DATE-TIME:20260522T065000Z DTEND;VALUE=DATE-TIME:20260522T072000Z DTSTAMP;VALUE=DATE-TIME:20260530T132724Z UID:indico-contribution-556-2468@indico.itp.ac.cn DESCRIPTION:Speakers: Huiyu Zhu (Institute for Basic Science)\nRotating bl ack holes can form dense boson clouds through superradiant instability\, m aking Kerr black holes a powerful probe of ultralight massive bosons. Prev ious studies of black hole superradiance have often treated bosonic fields classically\, leaving open questions about how particles are produced and how the clouds grow over time. In this work\, we canonically quantize a m assive scalar field around a Kerr black hole\, providing a fully quantum d escription of black hole superradiance. We show that the evolution of the particle number in the cloud\, as well as the energy and angular momentum of the scalar field\, can be consistently explained within the standard fr amework of quantum field theory in curved spacetime. Furthermore\, we prov e that the growth of the cloud occurs independently of the choice of initi al state. We also explore several phenomena related to a massive scalar fi eld in a rotating black hole spacetime\, including Hawking radiation\, adi abatic backreaction on the black hole spin\, and the direction of level tr ansitions in the presence of self-interactions of the field. Our analysis provides a consistent quantum-mechanical perspective that includes all the se phenomena.\n\nhttps://indico.itp.ac.cn/event/419/contributions/2468/ LOCATION:Small Lecture Hall\, Chongqing University Library (图书馆小 报告厅) 1F-9 URL:https://indico.itp.ac.cn/event/419/contributions/2468/ END:VEVENT BEGIN:VEVENT SUMMARY:The Nonlinear Tails of Black Hole Ringdown DTSTART;VALUE=DATE-TIME:20260522T061000Z DTEND;VALUE=DATE-TIME:20260522T065000Z DTSTAMP;VALUE=DATE-TIME:20260530T132724Z UID:indico-contribution-556-2462@indico.itp.ac.cn DESCRIPTION:Speakers: Sam Wong (City University of Hong Kong)\nBlack hole perturbation theory is a cornerstone of gravitational wave science\, provi ding a powerful framework to test General Relativity in the strong-field r egime and to characterize the final remnant of a binary merger. The final "ringdown" phase\, where the newly formed black hole settles into its stat ionary state\, is a particularly clean probe of its fundamental properties . In this talk\, I will begin by reviewing the essential structure of the Green's function in black hole perturbation theory\, which governs the res ponse of the black hole to any disturbance. I will then present our main r esult on the late-time behavior of gravitational waves\, demonstrating the existence of non-linearly generated power-law tails that dominate after t he initial ringdown signal has decayed. We show that this late-time tail i s a generic and robust feature for spinning black holes\, carrying importa nt information about the nonlinear nature of spacetime dynamics. If time p ermits\, I will also briefly discuss the connection between these nonlinea r phenomena and the behavior of tidal Love numbers during the inspiral pha se.\n\nhttps://indico.itp.ac.cn/event/419/contributions/2462/ LOCATION:Small Lecture Hall\, Chongqing University Library (图书馆小 报告厅) 1F-9 URL:https://indico.itp.ac.cn/event/419/contributions/2462/ END:VEVENT BEGIN:VEVENT SUMMARY:On cosmological properties of black-hole hair in linearly coupled scalar–Gauss–Bonnet theory DTSTART;VALUE=DATE-TIME:20260522T053000Z DTEND;VALUE=DATE-TIME:20260522T061000Z DTSTAMP;VALUE=DATE-TIME:20260530T132724Z UID:indico-contribution-556-2438@indico.itp.ac.cn DESCRIPTION:Speakers: Dražen Glavan (Institute of Physics of the Czech Ac ademy of Sciences)\nWe investigate the superhorizon behavior of scalar hai r sourced by black holes in de Sitter spacetime in the linearly coupled sh ift-symmetric scalar--Gauss--Bonnet theory. This hair exhibits both spatia l and temporal growth\, which has been suggested to be problematic. We sho w that this growth is expected\, as it is not a special consequence of the black hole\, but instead follows from the dynamics of a minimally coupled massless scalar field in expanding de Sitter spacetime. Moreover\, it is not specific to black holes\, but also arises for a point scalar charge in de Sitter\, indicating that a scalarized black hole acts effectively as a localized subhorizon source of scalar perturbations. Backreaction\, when important\, first arises on subhorizon scales and does not by itself elimi nate the superhorizon profile. The time-dependent scalar hair also carries a steady outward energy flux\, which helps explain the difficulties encou ntered in attempts to construct self-consistent static solutions.\n\nhttps ://indico.itp.ac.cn/event/419/contributions/2438/ LOCATION:Small Lecture Hall\, Chongqing University Library (图书馆小 报告厅) 1F-9 URL:https://indico.itp.ac.cn/event/419/contributions/2438/ END:VEVENT BEGIN:VEVENT SUMMARY:FoPTs\, PBHs\, SIGWs\, and SWs from early Universe DTSTART;VALUE=DATE-TIME:20260522T032000Z DTEND;VALUE=DATE-TIME:20260522T040000Z DTSTAMP;VALUE=DATE-TIME:20260530T132724Z UID:indico-contribution-556-2461@indico.itp.ac.cn DESCRIPTION:Speakers: Shao-Jiang Wang ( Institute of Theoretical Physics\, Chinese Academy of Sciences)\nIn this talk\, I will first introduce our r ecent progress in first-order phase transitions\, in particular\, generati ons of density perturbations\, formations of PBHs\, associated scalar-indu ced gravitational waves\, and productions of sound waves from gravitationa l instability.\n\nhttps://indico.itp.ac.cn/event/419/contributions/2461/ LOCATION:Small Lecture Hall\, Chongqing University Library (图书馆小 报告厅) 1F-9 URL:https://indico.itp.ac.cn/event/419/contributions/2461/ END:VEVENT BEGIN:VEVENT SUMMARY:Unified Origin of Primordial Black Hole Dark Matter and Nanohertz Gravitational Waves DTSTART;VALUE=DATE-TIME:20260522T024000Z DTEND;VALUE=DATE-TIME:20260522T032000Z DTSTAMP;VALUE=DATE-TIME:20260530T132724Z UID:indico-contribution-556-2450@indico.itp.ac.cn DESCRIPTION:Speakers: Shi Pi (Institute of Theoretical Physics\, Chinese A cademy of Sciences)\nRecent high-cadence observations by Subaru-HSC have i dentified a population of ultrashort-timescale microlensing events\, provi ding a compelling window for planet-mass primordial black holes (PBHs) to constitute the entirety of dark matter. In this Letter\, we demonstrate th at this PBH population and the nanohertz stochastic gravitational-wave (GW ) background reported by pulsar timing arrays (PTAs) can be naturally unif ied by a single primordial origin: a broad\, nearly-flat enhancement of th e curvature power spectrum with an amplitude of O ( 1 0 − 2 ) O(10 −2 ). The resulting PBH mass function spans the planet-to-solar mass range\, while remaining consistent with all current observational constraints. Thi s unified PBH--induced-GW framework makes concrete multi-messenger predict ions\, which can be decisively scrutinized by forthcoming microlensing sur veys\, next-generation PTAs\, space-borne interferometers\, precision astr ometry\, and laser ranging experiments.\n\nhttps://indico.itp.ac.cn/event/ 419/contributions/2450/ LOCATION:Small Lecture Hall\, Chongqing University Library (图书馆小 报告厅) 1F-9 URL:https://indico.itp.ac.cn/event/419/contributions/2450/ END:VEVENT BEGIN:VEVENT SUMMARY:Learning Gravity from Data: Model-Independent Reconstruction of th e Cosmic Expansion and Modified Gravity Theories DTSTART;VALUE=DATE-TIME:20260522T020000Z DTEND;VALUE=DATE-TIME:20260522T024000Z DTSTAMP;VALUE=DATE-TIME:20260530T132724Z UID:indico-contribution-556-2434@indico.itp.ac.cn DESCRIPTION:Speakers: Konstantinos Dialektopoulos (University of Malta)\nT he standard cosmological model is under increasing observational pressure. Persistent tensions in the Hubble constant and the growth of structure su ggest either unaccounted systematics or genuine new physics beyond ΛCDM — and distinguishing between these possibilities demands data analysis m ethods that do not smuggle in theoretical priors through the back door. In this talk\, I present a programme of model-independent reconstruction of late-time cosmology using machine learning to probe both the expansion his tory of the Universe and the underlying theory of gravity.\n\nhttps://indi co.itp.ac.cn/event/419/contributions/2434/ LOCATION:Small Lecture Hall\, Chongqing University Library (图书馆小 报告厅) 1F-9 URL:https://indico.itp.ac.cn/event/419/contributions/2434/ END:VEVENT END:VCALENDAR