BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Little Red Dots: The Wandering Black Holes DTSTART;VALUE=DATE-TIME:20261024T060000Z DTEND;VALUE=DATE-TIME:20261024T062000Z DTSTAMP;VALUE=DATE-TIME:20261024T233701Z UID:indico-contribution-653-3063@indico.itp.ac.cn DESCRIPTION:Speakers: Yu Wang (ICTP)\nhttps://indico.itp.ac.cn/event/427/c ontributions/3063/ LOCATION: URL:https://indico.itp.ac.cn/event/427/contributions/3063/ END:VEVENT BEGIN:VEVENT SUMMARY:Probing Memory-Burdened Primordial Black Holes with Multi-Messenge r Observations DTSTART;VALUE=DATE-TIME:20261024T073000Z DTEND;VALUE=DATE-TIME:20261024T075000Z DTSTAMP;VALUE=DATE-TIME:20261024T233701Z UID:indico-contribution-653-3013@indico.itp.ac.cn DESCRIPTION:Speakers: Xiu-hui Tan (Institute of Theoretical Physics\, CAS) \nThe memory burden (MB) effect can dramatically slow black hole evaporati on once half of the initial mass is radiated\, allowing very light primord ial black holes (PBHs) to persist today as dark matter (DM). We probe this scenario across three complementary messengers.\n\nUsing LHAASO ultra-hig h-energy gamma-ray spectra of four Galactic sources\, we constrain PBHs wi th masses 10^9 g. From 10 years of IceCube muon-track data and 14 dwarf sp heroidal galaxies with D-factor uncertainties treated via a profile likeli hood\, we derive neutrino limits on the PBH abundance. The cosmic-ray sign al from memory-burdened PBHs is also considered but yields weaker constrai nts.\n\nIn all channels no significant excess over background is found. Th e gamma-ray and neutrino probes provide independent and complementary limi ts on the MB scenario\; the neutrino results improve substantially on prev ious work in the k=1 case\, while the k=2 case and the cosmic-ray channel remain less constraining due to limited instrumental sensitivity in the re levant energy ranges. Our combined analysis thus significantly narrows the allowed parameter space for PBH dark matter under the MB effect.\n\nhttps ://indico.itp.ac.cn/event/427/contributions/3013/ LOCATION: URL:https://indico.itp.ac.cn/event/427/contributions/3013/ END:VEVENT BEGIN:VEVENT SUMMARY:Methods for Detecting Gravitational Waves from mini-Extreme-Mass-R atio Inspirals: A Spectral-Leakage-Aware Framework DTSTART;VALUE=DATE-TIME:20261025T075000Z DTEND;VALUE=DATE-TIME:20261025T081000Z DTSTAMP;VALUE=DATE-TIME:20261024T233701Z UID:indico-contribution-653-3014@indico.itp.ac.cn DESCRIPTION:Speakers: Zixuan Wang (ICTP-AP)\nMini-extreme-mass-ratio inspi rals (mini-EMRIs)\, in which a subsolar-mass compact object orbits a much heavier compact object\, are long-duration gravitational-wave sources of i nterest to ground-based detectors. Their signals can remain in band for ho urs to years\, making fully coherent matched-filter searches computational ly expensive. Semicoherent time-frequency searches reduce this cost by div iding the data into short Fourier segments and combining segment-level pow ers or related statistics. Conventional implementations\, however\, often require the signal to remain approximately monochromatic within each segme nt\, thereby limiting the coherent duration when the signal frequency evol ves appreciably.\n\nWe extend the ΣTrack framework beyond the quasi-monoc hromatic regime in two steps. First\, we derive a linear-chirp model for t he spectral leakage produced within a short-time Fourier segment. Second\, we construct the $\\Sigma R$ statistic\, a weighted sum of power ratios o ver a finite multi-pixel track\, to recover signal power distributed among neighboring frequency bins. The resulting sensitivity model further motiv ates a frequency-layered search in which the coherent duration is optimize d separately in different frequency intervals.\n\nFor a fiducial $(1.5\,10 ^{-5})\\\,M_\\odot$ mini-EMRI and under the assumptions of our analytic co mparison\, the optimized $\\Sigma R$ configuration yields an effective det ection volume about an order of magnitude larger than that of the Hough-li ke reference statistic considered here.\nMore broadly\, the proposed frame work provides a systematic way to incorporate spectral leakage into semico herent time-frequency statistics and to optimize the coherence time across the signal band\, thereby extending power-track searches to long-duration signals with appreciable frequency evolution.\n\nhttps://indico.itp.ac.cn /event/427/contributions/3014/ LOCATION: URL:https://indico.itp.ac.cn/event/427/contributions/3014/ END:VEVENT BEGIN:VEVENT SUMMARY:A continuous wave window into neutron star structure DTSTART;VALUE=DATE-TIME:20261025T073000Z DTEND;VALUE=DATE-TIME:20261025T075000Z DTSTAMP;VALUE=DATE-TIME:20261024T233701Z UID:indico-contribution-653-3019@indico.itp.ac.cn DESCRIPTION:Speakers: Ayush Hazarika (International Centre for Theoretical Physics Asia-Pacific (ICTP-AP)\, University of Chinese Academy of Science s)\nEvery rapidly spinning neutron star with slight asymmetry would broadc ast a continuous hum of gravitational waves (GW). None of these signals ha s been detected yet\, but the silence itself is measurable: searches now s et upper limits on the GW amplitude of dozens of known pulsars\, and for a growing subset those limits dig below the energy budget available from th e stars' own spin-down. We ask what this kind of data\, can say about the interior of a neutron star. The amplitude of the continous signal depends on how much matter the star carries in its deformation and how that matter is distributed\, its moment of inertia\, which in turn is fixed by the un known equation of state of dense matter. This opens a route to the neutron star mass-radius relation that is fully independent of the X-ray pulse-pr ofile and binary-merger measurements that anchor current constraints. We b uild a hierarchial Bayesian pipeline that propagates simulated amplitude l imits\, treated consistently as non-detections\, through stellar-structure calculations to the mass-radius plane\, marginalizing over the unknown de formations of the pulsar population. Rather than claiming a new measuremen t\, we chart the sensitivity frontier: how deep continuous-wave searches m ust go before they begin to weigh in on dense matter on their own.\n\nhttp s://indico.itp.ac.cn/event/427/contributions/3019/ LOCATION: URL:https://indico.itp.ac.cn/event/427/contributions/3019/ END:VEVENT BEGIN:VEVENT SUMMARY:Probing gravitational waves with the orbital angular momentum of l ight DTSTART;VALUE=DATE-TIME:20261025T064000Z DTEND;VALUE=DATE-TIME:20261025T070000Z DTSTAMP;VALUE=DATE-TIME:20261024T233701Z UID:indico-contribution-653-3020@indico.itp.ac.cn DESCRIPTION:Speakers: Haorong Wu (Wuhan University)\nWe introduce an alter native approach to gravitational-wave (GW) detection in which GW informati on is encoded in the orbital angular momentum (OAM) states of photons. Sta rting from the propagation of vortex light in linearized gravity\, we show that interaction with a GW induces transitions from an initial photon OAM state to neighboring OAM sidebands\, providing a different optical observ able of spacetime perturbations. Building on this interaction\, we develop a GW detection framework in which the complex amplitudes of the induced O AM sidebands are measured using parametrized quantum state tomography. A V -shaped configuration provides sufficient independent degrees of freedom t o resolve all seven wave parameters characterizing a GW. We further invest igate the detectability of this approach by constructing a noise budget ov er the frequency range from 1 mHz to 100 Hz. The symmetry properties of th e OAM states allow the GW signal to appear predominantly in the differenti al mode\, while technical noise enters primarily through the common mode\, enabling its suppression through balanced detection. Our analysis further shows that a compact\, short-arm configuration can reduce mode-crosstalk noise without sacrificing the GW response. Together\, these results establ ish a framework for probing GWs through the spatial-mode Hilbert space of light and motivate OAM-based sensing as a complementary approach to future GW detection.\n\nhttps://indico.itp.ac.cn/event/427/contributions/3020/ LOCATION: URL:https://indico.itp.ac.cn/event/427/contributions/3020/ END:VEVENT BEGIN:VEVENT SUMMARY:Multi-Band Constraints on Cosmic Strings: Unifying Harmonic and Bu rst Spectra DTSTART;VALUE=DATE-TIME:20261025T062000Z DTEND;VALUE=DATE-TIME:20261025T064000Z DTSTAMP;VALUE=DATE-TIME:20261024T233701Z UID:indico-contribution-653-3017@indico.itp.ac.cn DESCRIPTION:Speakers: Hansong Zhang (ICTP-AP)\nCosmic-string loops generat e a broadband gravitational-wave background (GWB) that is typically modele d via two distinct formalisms: a discrete harmonic expansion\, commonly us ed in pulsar-timing-array (PTA) studies\, and a continuous burst superposi tion\, employed in ground-based GWB searches. In this work\, we formally u nify the two formalisms\, showing that they provide discrete and continuou s representations of the same underlying radiation process and converge on the scale-invariant spectrum plateau. On the rising low-frequency branch\ , where the first few harmonics dominate\, the discrete nature becomes imp ortant\, causing the two formalisms to diverge. Within this unified framew ork\, the spectral calculation is more consistent across frequency bands\, enabling multi-band inference. Leveraging this physical insight\, we perf orm joint Bayesian inference across four representative loop-distribution models using the NANOGrav\, EPTA\, and LIGO--Virgo--KAGRA (LVK) datasets. By jointly sampling the string tension $G\\mu$ alongside the average cusp and kink numbers $\\{N_c\, N_k\\}$\, the loop-radiation uncertainties are accounted for. We find that employing the harmonic expansion strengthens t he LVK bounds by $21\\%-31\\%$ for three of these models. Additionally\, t he stringent LVK bounds preclude three of these models from explaining the observed PTA common signal. For the sole surviving model\, our multi-band analysis improves the inferred limit on $G\\mu$.\n\nhttps://indico.itp.ac .cn/event/427/contributions/3017/ LOCATION: URL:https://indico.itp.ac.cn/event/427/contributions/3017/ END:VEVENT BEGIN:VEVENT SUMMARY:Evo-MCTS: Gravitational-Wave Algorithm Search and Lessons for AI-A ssisted Physics DTSTART;VALUE=DATE-TIME:20261025T060000Z DTEND;VALUE=DATE-TIME:20261025T062000Z DTSTAMP;VALUE=DATE-TIME:20261024T233701Z UID:indico-contribution-653-3012@indico.itp.ac.cn DESCRIPTION:Speakers: He Wang (ICTP-AP\, UCAS)\nThis talk presents Evo-MCT S (arXiv:2508.03661)\, a framework combining large language models\, Monte Carlo tree search\, and evolutionary optimization for automated algorithm discovery\, using gravitational-wave signal searches as a case study. Thr ough analyses of search trajectories and subsequent audits\, we examine ho w benchmark design influences optimization and how independent validation and physical consistency checks can distinguish improvements in evaluation metrics from genuine scientific advances. Building on these findings\, we explore the potential of large language models in theoretical physics\, i ncluding the search for exact black-hole solutions through symbolic comput ation and formal verification in Lean\, and discuss broader opportunities and challenges for AI-assisted scientific research.\n\nhttps://indico.itp. ac.cn/event/427/contributions/3012/ LOCATION: URL:https://indico.itp.ac.cn/event/427/contributions/3012/ END:VEVENT BEGIN:VEVENT SUMMARY:Searches and Latest Results for the Isotropic Gravitational-Wave B ackgrounds with LIGO-Virgo-KAGRA detectors DTSTART;VALUE=DATE-TIME:20261024T081000Z DTEND;VALUE=DATE-TIME:20261024T083000Z DTSTAMP;VALUE=DATE-TIME:20261024T233701Z UID:indico-contribution-653-3015@indico.itp.ac.cn DESCRIPTION:Speakers: Ruhan Rao (UCAS\, ictp-ap)\nThe gravitational-wave b ackground (GWB) is a superposition of individually unresolved gravitationa l-wave (GW) signals arising from both astrophysical and cosmological sourc es accumulated throughout cosmic history. We refer to the GWB as “stocha stic” as it can be characterized statistically as a mean zero stochastic field. For the isotropic GWB search considered here\, the GWB is further assumed to be stationary\, isotropic\, and unpolarized. Detecting a stocha stic GWB can provide information about astrophysical source populations an d processes in the early Universe. In this talk\, I will introduce the ana lysis methods\, including the cross-correlation spectra\, frequency estim ator and parameter estimation\, and present the latest results using LIGO –Virgo–KAGRA data through April 2025.\n\nhttps://indico.itp.ac.cn/even t/427/contributions/3015/ LOCATION: URL:https://indico.itp.ac.cn/event/427/contributions/3015/ END:VEVENT BEGIN:VEVENT SUMMARY:Probing Inflationary Origins of Primordial Black Holes with LIGO-V irgo-KAGRA O1-O4a data DTSTART;VALUE=DATE-TIME:20261024T075000Z DTEND;VALUE=DATE-TIME:20261024T081000Z DTSTAMP;VALUE=DATE-TIME:20261024T233701Z UID:indico-contribution-653-3016@indico.itp.ac.cn DESCRIPTION:Speakers: 迈 乔 (中国科学院大学 国际理论物理中 心（亚太地区）)\nLarge primordial curvature perturbations can produ ce primordial black holes (PBHs) and inevitably generate a scalar-induced stochastic gravitational-wave background upon horizon re-entry. In this ta lk\, based on our recent work arXiv:2609.12867\, we will present constrain ts from the combined LIGO–Virgo–KAGRA O1–O4a data on two representat ive inflationary mechanisms for producing such perturbations: ultra-slow-r oll inflation and an inflationary phase transition. We find no evidence fo r either signal and derive 95% credible upper limits on the curvature-spec trum amplitude over the frequency range accessible to ground-based interfe rometers. Because PBH abundance depends exponentially on the perturbation amplitude\, even a modest improvement in the amplitude constraint can tran slate into orders-of-magnitude stronger limits on PBH formation. The resul ting bounds probe PBH abundances far below unity and can surpass conventio nal constraints. Importantly\, the gravitational-wave signal preserves inf ormation about PBH formation even when the PBHs are too rare for direct se arches or have already evaporated. These results demonstrate that stochast ic gravitational-wave observations provide a powerful and complementary pr obe of small-scale inflationary physics\, with future interferometers exte nding the reach to a broader range of inflationary epochs and PBH masses.\ n\nhttps://indico.itp.ac.cn/event/427/contributions/3016/ LOCATION: URL:https://indico.itp.ac.cn/event/427/contributions/3016/ END:VEVENT BEGIN:VEVENT SUMMARY:Silk damping in induced gravitational waves: a novel probe of new physics DTSTART;VALUE=DATE-TIME:20261024T064000Z DTEND;VALUE=DATE-TIME:20261024T070000Z DTSTAMP;VALUE=DATE-TIME:20261024T233701Z UID:indico-contribution-653-3018@indico.itp.ac.cn DESCRIPTION:Speakers: Yu Yan-Heng (HIAs\, UCAS)\nThe early universe is a n atural laboratory for high-energy physics\, and gravitational waves\, as d irect probes of this epoch\, inherently carry rich information related to high-energy physics. Silk damping\, resulting from dissipation in the cosm ic fluid\, is a significant physical phenomenon in the early universe. In this talk\, I will introduce our first study on Silk damping in induced gr avitational waves. Silk damping notably suppresses the spectrum of induced gravitational waves on scales comparable to a diffusion scale at the deco upling of weakly-interacting particles. This characteristic suppression of fers a novel and general observable for detecting the underlying particle interaction\, especially for those mediated by heavy gauge bosons beyond t he Standard Model. We anticipate that pulsar timing arrays are sensitive t o gauge bosons with masses ∼ 10³−10⁴ GeV\, while space- and ground- based interferometers to those with masses ∼ 10⁷−10¹² GeV\, leadin g to essential complements to traditional high-energy physics experiments. \n\nhttps://indico.itp.ac.cn/event/427/contributions/3018/ LOCATION: URL:https://indico.itp.ac.cn/event/427/contributions/3018/ END:VEVENT BEGIN:VEVENT SUMMARY:The Generation and Detection of Chiral Gravitational Wave Backgrou nds DTSTART;VALUE=DATE-TIME:20261024T062000Z DTEND;VALUE=DATE-TIME:20261024T064000Z DTSTAMP;VALUE=DATE-TIME:20261024T233701Z UID:indico-contribution-653-2988@indico.itp.ac.cn DESCRIPTION:Speakers: Yun-Long Zhang (NAOC(National Astronomical Observato ries\, CAS))\nChiral gravitational wave backgrounds are predicted in many well-motivated mechanisms. We investigate the detection of Chiral GWBs usi ng a network of detectors under arbitrary configurations. We also propose a dipole pulsar timing array\, which demonstrates sensitivity to Chiral gr avitational wave backgrounds from the nanohertz to microhertz regime.\n\nh ttps://indico.itp.ac.cn/event/427/contributions/2988/ LOCATION: URL:https://indico.itp.ac.cn/event/427/contributions/2988/ END:VEVENT END:VCALENDAR