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The 6th BRICS-AGAC Symposium 2026, Hangzhou, China

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Zhejiang Hotel

Zhejiang Hotel

No. 278, Santaishan Road, Hangzhou, 310007
Rong-Gen Cai (Ningbo University)
Description

The BRICS-AGAC Symposium

Considering that notable progresses have been made in the studies of gravitation, astrophysics, and cosmology among BRICS countries in the past decades, the BRICS Association on Gravity, Astrophysics, and Cosmology (BRICS-AGAC) was established at the end of 2016 to promote further collaborations between the member countries. This year, the BRICS-AGAC Symposium will come back to its founding place--Hangzhou.

Welcome to the 6th Symposium of the BRICS Association on Gravity, Astrophysics, and Cosmology (BRICS-AGAC Symposium 2026), to be held on November 6th-10th, 2026, near the West Lake in Zhejiang Hotel, Hangzhou city, Zhejiang Province, China. This symposium continues the tradition of fostering collaboration and sharing cutting-edge research among scientists from BRICS nations and around the globe.

The registration fee for each participant is 2000 CNY (including conference materials, participation in all sessions, coffee breaks, meals, and banquet). We will arrange the accommodations in the Zhejiang Hotel, and the accommodation fee will be paid by the participant.

Past BRICS-AGAC Symposiums

The 5th BRICS-AGAC Symposium @ 2025/12/09-12 @ Federal University of Paraíba (UFPB), João Pessoa, Brazil 

https://bricsagac.com.br

The 4th BRICS-AGAC Symposium @ 2024/12/17-19 @ Shree Guru Gobind Singh Tricentenary University (SGT University), located in Budhera, Gurugram, Haryana, India 

https://ccsp.sgtuniversity.ac.in/BRICS-AGAC-2024/index.html

The 3rd BRICS-AGAC Symposium @ 2019/08/29-09/03 @ Kazan Federal Universirty, Kazan, Russia

https://kpfu.ru/physics/struktura/kafedry/kafedra-teorii-otnositelnosti-i-gravitacii/brics-agac-2019

The 2nd BRICS-AGAC Symposium @ 2018/10/22-28 @ University of KwaZulu-Natal, Durban, South Africa

https://acru.ukzn.ac.za/~brics-acg

https://za.china-embassy.gov.cn/dshdxwfb/2018/201811/t20181101_10406706.htm

The 1st BRICS-AGAC Symposium @ 2017/10/18-20 @ Yangzhou University, Yangzhou, China

https://cgc.yzu.edu.cn/info/1030/1286.htm

Time table & Venue

Registration: November 6th

Conference: November 7th-9th

Departure: November 10th

Venue: Zhejiang Hotel, Hangzhou, China

Accommodations

All participants will be arranged at Zhejiang Hotel as shown below, and do not believe any other acting representatives.

Zhejiang Hotel

No. 278, Santaishan Road, Hangzhou, 310007 

http://www.zhejianghotel.com/en/reservation.html

500 CNY/night

浙江宾馆

杭州三台山路278号 ，310007

http://www.zhejianghotel.com/cn/index.html

500 元/晚（如果超过报销标准请备注）

Scientific Organization Committee

  • Elcio Abdalla  (University of São Paulo, Brazil)
  • Kirill Bronnikov  (RUDN University & National Research Nuclear University, Russia)
  • Rong-Gen Cai  (Chairman, Ningbo University, China)
  • Bin Chen  (Ningbo University, China)
  • Dmitri V. Gal'tsov  (Moscow State University, Russia)
  • Roy Maartens  (University of the Western Cape, South Africa)
  • Jeff Murugan  (University of Cape Town, South Africa)
  • Pradyumn Kumar Sahoo  (Birla Institute of Technology and Science, India)
  • Mohammad Sami  (SGT University, India)
  • Lakshmanan Sriramkumar  (Indian Institute of Technology Madras, India)
  • Carlos Alexandre Wuensche  (INPE, São José, Brazil)

Local Organization Committee

  • Rong-Gen Cai (Ningbo University)
  • Bin Chen (Ningbo University)
  • Chao-Qiang Geng (Hangzhou Institute for Advanced Study, UCAS)
  • Hong-Sheng Hou (Hangzhou Normal University)
  • Li Li (Institute of Theoretical Physics, Chinese Academy of Sciences)
  • Sai Wang (Hangzhou Normal University)
  • Shao-Jiang Wang (Institute of Theoretical Physics, Chinese Academy of Sciences)
  • Tao Zhu (Zhejiang University of Technology)

Contact

For domestic matter: Jing Wang (王静: SLXY@ucas.ac.cn) from HIAS-UCAS

For foreign matter: Junyu Luo (罗隽彧: luojunyu@nbu.edu.cn) from Ningbo University

Organizers & Supporters

The conference has been funded by the Peng Huanwu Innovation Research Center for Theoretical Physics.

Institute of Theoretical Physics, Chinese Academy of Sciences

Ningbo University

Zhejiang University of Technology

Hangzhou Normal University

Hangzhou Institute for Advanced Study, UCAS

 

Participants
  • Aakanksha Basu
  • Adesh Meshram
  • Ahmad Albadawi
  • Aleksandr Dolgov
  • Alexey Toporensky
  • Amare Abebe
  • Andrew Beckwith
  • Andrew Fowlie
  • Andrew Miller
  • Arghyadeep Biswas
  • Atsuhisa Ota
  • Ayush Hazarika
  • Bharti Kaushik
  • Bin Chen
  • Boyu Zhang
  • Breno Loureiro Giacchini
  • Chang Feng
  • Chang LIU
  • Changkai Chen
  • Chao-Qiang Geng
  • Chen Tan
  • Chengcheng Liu
  • Chi Tian
  • Cong Zhang
  • Dandan Cui
  • Daniel Fikadu Assefa
  • Darshan Kumar
  • De-Cheng Zou
  • DEBADRI BHATTACHARJEE
  • Dhiraj Kuniyal
  • Di Li
  • Di Li
  • Dmitry Gorbunov
  • Dong Lai
  • Dongyong Xi
  • Ekaterina Pozdeeva
  • Elcio Abdalla
  • Elcio Abdalla
  • Elena Arbuzova
  • Fabio Marchesoni
  • Fu-Wen Shu
  • Gaoping Long
  • Gen Ye
  • Guanhao Sun
  • Hai-Shan Liu
  • Haiyuan Feng
  • Hamza Rehman
  • Hang Liu
  • Hao Xu
  • Haojie Lin
  • Haoran Xu
  • Haryanto Mangaratua Siahaan
  • Hemwati Nandan
  • Hilaal Alam
  • Hongguang Liu
  • hongwei Tan
  • Huan Yang
  • Hui Tong
  • Hui-Min Fan
  • Igor Bulyzhenkov
  • INDU KALPA DIHINGIA
  • Ioannis Soranidis
  • Ji Li
  • Jia-Nan Chi
  • Jia-Rui Sun
  • Jia-Xi Feng
  • Jiajun Zhang
  • Jian-Ming Yan
  • Jianbo Lu
  • Jiangying DONG
  • Jie Wu
  • Jie Yang
  • JIE ZHENG
  • Jieci Wang
  • Jin Li
  • Jin Qiao
  • Jingbo Wang
  • Jingjie Meng
  • JITUMANI KALITA
  • Jizhong Shen
  • Jun Zhang
  • Kiran D M
  • Kohei Kamada
  • Leijian Wang
  • Lerothodi Leeuw
  • Li Hu
  • Li Li
  • li zhao
  • Long-Xing Huang
  • LUCIANO Barosi
  • Manjeet Kunwar
  • Matti Jarvinen
  • Md Saddam Hussain
  • Mei-Ning Duan
  • Miguel Angel Martin Contreras
  • Mingshan Ding
  • Mohammad M. Sheikh-Jabbari
  • Mohit Thakre
  • Monis Naidoo
  • Muhammad Rizwan Shahzad
  • Nakshatra Gaikwad
  • Oleg Zaslavskiy
  • Owais Farooq
  • Peizhi Du
  • Peng-Bo Ding
  • PRADIP KUMAR CHATTOPADHYAY
  • Pradyumn Sahoo
  • Prashant Kocherlakota
  • Praveen Kumar Dhankar
  • Priya Shah
  • Puxun Wu
  • Qian Chen
  • Qiang Wu
  • Qiyuan Pan
  • ran ding
  • Renjie Wang
  • Rohit Kumar
  • Runyu Gao
  • Ruoceng Wu
  • Sagar Kumar Maity
  • Sai Wang
  • Saikat Chakraborty
  • Saiya Zhang
  • Sandip Singha
  • Sergey Mironov
  • Sergey Vernov
  • SHAO CAIYING
  • Shao-Jiang Wang
  • Shao-Wen Wei
  • Shaoqi Hou
  • Shaoqin Wu
  • Shoulong Li
  • Si-Jiang Yang
  • Siham Kalli
  • Sijia LIU
  • Song He
  • Songbai Chen
  • Subhajit Saha
  • Sumanta Chakraborty
  • Tao Yang
  • Tao Zhu
  • Udaykrishna Thattarampilly
  • Ujjwal Kumar Upadhyay
  • VIKTOR KRYM
  • Wei-Jia Li
  • Wen Zhao
  • Wencong Gan
  • Wenyuan Ai
  • Williet Nyuywiyni Dinka
  • Xian Gao
  • Xiang-Qian Li
  • Xiao-Jun Yue
  • Xiao-Mei Kuang
  • Xiaobin Sui
  • Xiaofeng YANG
  • Xiaojun Bi
  • Xiaoning Wu
  • Xiaotian Zhang
  • Xinyang Jin
  • Xuelei Chen
  • Xujie Zhu
  • Yan Peng
  • Yan-Rong Li
  • Yashi Tiwari
  • Yi Pang
  • Yi-Ming Hu
  • Yifan Wang
  • Ying Wang
  • Yiqing Chu
  • Yiyang Wang
  • Yu Sang
  • Yu-Sen An
  • Yu-Xiao Liu
  • Yu-Xuan Li
  • Yuanzhang Cui
  • Yuchen Zhang
  • Yucheng Wang
  • Yue Fu
  • Yue-Lin Sming Tsai
  • Yuewei Wen
  • Yujie Tan
  • Yun Fang
  • Yun-Long Zhang
  • Yuxuan Peng
  • Zehua Tian
  • Zhao Li
  • Zhen-Ming Xu
  • Zhi-Zhang Peng
  • Zi-Qing Xiao
  • Zong-Kuan Guo
  • 席民 梁
  • 静 王
Contact: Shao-Jiang Wang
  • Friday, 6 November
    • 12:00 → 21:00
      Registration
  • Saturday, 7 November
    • 08:00 → 08:30
      Ceremony: Opening Ceremony
    • 08:30 → 12:00
      Plenary Session
      • 08:30
        A FAST View of Fast Radio Bursts 45m
        Speaker: Prof. Di Li (Tsinghua University)
      • 09:15
        The BINGO-ABDUS project: DM and DE cosmological problem with a possible description in field theory 45m
        Speaker: Prof. Elcio Abdalla (University of Sao Paulo)
      • 10:00
        Break 30m
      • 10:30
        Physics and Astrophysics of Merging Compact Binaries 45m
        Speaker: Prof. Dong Lai (Tsung-Dao Lee Institute, Shanghai Jiao Tong University)
      • 11:15
        Testing the Dark Sector at Fixed H0 and S8​: The Cosmological Consistency Triangle 45m
        Speaker: Prof. Amare Abebe (North-West University)
    • 12:00 → 14:00
      Lunch 2h
    • 14:00 → 18:00
      Parallel-Astrophysics
      • 14:00
        GW Astronomy with TianQin 30m

        The millihertz gravitational-wave band offers a new view of compact objects and black holes across cosmic history. TianQin, a planned space-based observatory, will explore this band through long-duration observations. In this talk, I will discuss its astrophysical prospects, from Galactic double white dwarfs and stellar-mass black hole binaries to massive black hole mergers and extreme-mass-ratio inspirals. These sources address questions at different scales: how compact binaries form and evolve, how massive black holes grow through mergers, and how stellar remnants move within galactic nuclei. I will also consider how joint observations with other gravitational-wave detectors and electromagnetic telescopes could improve source characterization and enable multi-messenger studies. I will conclude by introducing the proposed TianQin Mock Data Challenge (MDC), currently in preparation, and its potential role in developing and testing the data-analysis methods needed to realize these science goals.

        Speaker: Prof. Yi-Ming Hu
      • 14:30
        Clock Noise Suppression in Space-Based Gravitational Wave Detection 30m

        Space-based gravitational wave detection (e.g., LISA, Taiji, and TianQin) relies on ultra-high-precision inter-satellite laser interferometry. However, clock noise is approximately two orders of magnitude higher than the detector noise floor, which severely limits the overall detection sensitivity and becomes a critical constraint for space-based gravitational wave observatories. To address this challenge, this presentation reports our recent progress in both theoretical and experimental studies on clock noise suppression.

        Speaker: Yujie Tan (Huazhong University of Science and Technology)
      • 15:00
        Gravitational-Wave Signatures of Source Motion: Probing Dynamical Environments and Merger Recoils 30m

        The motion of black-hole systems can leave distinctive imprints on gravitational-wave signals, offering a unique window into both their surrounding environments and merger dynamics. In this talk, I will discuss two representative effects associated with black-hole motion across different stages of binary evolution. First, I will consider stellar-mass binary black holes orbiting a supermassive black hole in galactic nuclei, where the long-term orbital motion produces characteristic modulations in the observed gravitational-wave signal. These modulations provide an opportunity to probe the mass, spin, and orientation of the central supermassive black hole, as well as the dynamical configuration of the system. I will then turn to the recoil of the merger remnant caused by asymmetric gravitational-wave emission. Such recoil signatures can be imprinted directly in the gravitational-wave signal and may be detectable with next-generation ground- and space-based observatories. Our forecasts indicate that these observations can substantially improve our ability to measure supermassive black-hole properties and characterize black-hole merger dynamics. Together, these studies highlight the broader role of source motion in gravitational-wave astronomy: rather than being a secondary correction, it can serve as a powerful probe of otherwise inaccessible astrophysical information and open new opportunities for studying black holes across multiple scales and frequency bands.

        Speaker: Prof. Li Jin (Chongqing University)
      • 15:30
        Nonlinear Quasinormal Modes in the Ringdown of GW250114: Observational Evidence for Nonlinear Gravitational Waves 30m

        The ringdown signal following a binary black hole merger offers a crucial avenue for investigating black hole properties and testing General Relativity in strong-field regimes. Beyond linear quasinormal modes, General Relativity predicts the existence of second-order quasinormal modes arising from the nonlinear coupling of gravitational waves. This talk presents an analysis of the ringdown signal from the gravitational-wave event GW250114, demonstrating observational evidence for second-order quasinormal modes. Through a systematic calculation of coupling coefficients for the first ten second-order modes, and the application of a novel data analysis method, we find a Bayes factor of 62 supporting the presence of these nonlinear modes at a selected ringdown starting time. A zero-amplitude hypothesis is excluded with a significance of 3.4 sigma, and the inferred amplitudes and complex frequencies are consistent with General Relativity predictions. We will discuss the analysis methodology, key results, and their physical implications, illustrating how black hole spectroscopy can be extended into the nonlinear regime and providing a new observational window for testing the nonlinear structure of General Relativity.

        Speaker: Yifan Wang
      • 16:00
        Break 30m
      • 16:30
        Astrophysical lessons from merging binary black holes: gap and highly spinning subpopulation 30m

        Uncovering the origins of binary black holes through gravitational-wave detections provides a powerful probe of the evolution, interactions, and environments of massive stars. Stellar theory predicts a forbidden range of black-hole masses between 50-130Msun due to pair-instability supernovae. In this talk, I will present our latest observational evidence of the pair-instability gap in the distribution of black hole masses. While the gap is not present in the distribution of primary masses, it appears unambiguously in the distribution of secondary masses. The location of the gap lines up well with a previously identified transition in the binary black-hole spin distribution; binaries with primary components in the gap tend to spin more rapidly than those below the gap. We interpret these findings as evidence for a subpopulation of hierarchical mergers. I will also highlight the concurrent signatures of hierarchical mergers. If time permits, I will introduce the results of the astrophysical distributions of merging compact objects in the latest GWTC-5 LVK paper.

        Speaker: Mr Tong Hui (Monash University/CITA)
      • 17:00
        Gravitational wave lensing beyond geometric optics 30m
        Speaker: Dr Li Zhao (Peking Univ.)
      • 17:30
        A continuous wave window into neutron star structure 30m

        Every rapidly spinning neutron star with slight asymmetry would broadcast a continuous hum of gravitational waves (GW). None of these signals has been detected yet, but the silence itself is measurable: searches now set 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 the 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 unknown 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-profile and binary-merger measurements that anchor current constraints. We build a hierarchial Bayesian pipeline that propagates simulated amplitude limits, treated consistently as non-detections, through stellar-structure calculations to the mass-radius plane, marginalizing over the unknown deformations of the pulsar population. Rather than claiming a new measurement,
        we chart the sensitivity frontier: how deep continuous-wave searches must go before they begin to weigh in on dense matter on their own.

        Speaker: Ayush Hazarika (International Centre for Theoretical Physics Asia-Pacific (ICTP-AP), University of Chinese Academy of Sciences)
    • 14:00 → 18:00
      Parallel-Cosmology
      • 14:00
        Modified gravity and the cosmological tensions 30m

        Cosmological tensions are one of the central topics of modern cosmology. The most prominent is the Hubble tension in which the measured expansion rate of the Universe from distance ladder is more than $5 \sigma$ larger than that predicted by $\Lambda$CDM based on CMB. Recently, BAO observation from DESI also reports a $2 - 3 \sigma$ tension with $\Lambda$CDM which might point to evolving dark energy. In this talk I will discuss our recent research on the possible gravitational origin of these cosmological tensions. Starting from model independent reconstruction technique, we found that the DESI BAO observation can be well explained by non-minimal coupling between gravity and matter. Further study shows that the same non-minimal coupled gravity can also naturally explain the Hubble tension, hinting a common gravitational origin of the two major cosmological tensions.

        Speaker: Gen Ye (University of Chinese Academy of Sciences)
      • 14:30
        Tomography of cosmic birefringence induced by 3-form dark energy 30m

        3-form dark energy shows a similar behavior to but distinguishable one from that of a scalar field in an expanding universe, and its tensorial structure allows for unique couplings that cannot be experienced by canonical scalars.
        We here explore the possibility that 3-form dark energy can explain the cosmic birefringence angle β~0.3°, as suggested by observations of the CMB polarization.
        We consider two EFT-inspired couplings between the 3-form and the photon, finding a dimension-4 operator is a candidate explanation, moreover predicting a photon mass around the Hubble scale.
        The profiles for β(z) from the model can mimic those from ALP dark energy or ALP dark matter, or be distinguishable, depending on the field configuration in the early universe, which may be tested by precise measurements of CMB polarization or radio galaxies.

        Speaker: Kohei Kamada (HIAS-UCAS)
      • 15:00
        Can Distance Duality Violation Save Late-time Solutions to the Hubble Tension? 30m

        The discrepancy between early- and late-Universe determinations of the Hubble constant may point to physics beyond ΛCDM or to unaccounted-for systematics. Numerous late-time modifications to the expansion history have been proposed to alleviate this discrepancy, with limited success. Recent works have shown that, when the sound-horizon and supernova calibrations are held fixed,any purely late-time resolution requires a violation of the cosmic distance duality relation (CDDR). Recasting the tension in the $r_d–M_B$ plane, we show explicitly that distance duality, together with BAO and uncalibrated supernova data and a fixed sound-horizon calibration, determines $H_0$ independently of the late-time expansion history. We then test the viability of the required CDDR violation by separately constraining reciprocity violation and photon number non-conservation, deriving a new constraint on reciprocity-violating distortions of angular-diameter distances from BAO and cosmic-chronometer data. Combining this result with existing photon-number-conservation constraints, we find that the level of distance-duality violation needed to resolve the tension is strongly disfavoured by current data. We therefore conclude that, for fixed sound-horizon and supernova calibrations, no modification confined to the late-time expansion history—even one violating distance duality—can resolve the Hubble tension, pointing instead toward early-Universe physics or unresolved local systematics.

        Speaker: Yashi Tiwari (Institute of Theoretical Physics, Chinese Academy of Sciences)
      • 15:30
        Updated Constraints on Infrared Cutoff Models and Implications for CMB-BAO Tension 30m

        The nearly scale-invariant primordial power spectrum provides the standard initial conditions for cosmological perturbations. However, the largest observable scales remain only weakly constrained by current CMB measurements, leaving open the possibility of deviations from scale invariance, such as an infrared (IR) cutoff in the primordial spectrum. This possibility is further motivated by the persistence of large-scale CMB anomalies, most notably the low quadrupole power. Recently, IR cutoff scenarios have attracted renewed attention due to their potential interplay with reionisation features, which can partially alleviate the emerging CMB–BAO discrepancy within the $\Lambda$CDM framework following recent DESI observations. In this talk, I will discuss our recent work where we revisited several broad classes of phenomenologically motivated IR cutoff models using parametrised forms of the primordial power spectrum. I will present updated constraints on IR cutoff scenarios from recent CMB observations, discuss their implications for the CMB–BAO discrepancy, and comment on the status of large-scale CMB anomalies from a Bayesian perspective of anomaly statistics.

        Speaker: Dr Ujjwal Kumar Upadhyay (The Institute of Mathematical Sciences)
      • 16:00
        Break 30m
      • 16:30
        Human–AI Collaboration-Driven Cosmology Research 30m

        In modern cosmological research, using cosmological numerical simulations to study the evolution of the large-scale structure of the Universe has proven to be a highly effective technique. However, cosmological numerical simulations beyond the standard cosmological model require numerous modifications to existing cosmological simulation frameworks. They are technically complex and have a high entry barrier, so a large number of non-standard cosmological models cannot be effectively validated. In recent years, the development of artificial intelligence technologies represented by large language models has brought profound changes to scientific research; for example, large language models such as DeepSeek have rapidly spread across various areas of life. Based on the DeepSeek large language model, we developed an agent for cosmological numerical simulations. This agent uses multi-agent collaboration technology and integrates functions such as literature review, code analysis, and report generation, allowing users to generate complex cosmological numerical simulation software with a single sentence. After evaluation, we found that the agent can effectively avoid generating hallucinations and produce work guides with real productive capacity. Using these work guides, we automatically developed cosmological numerical simulation software for models including SIDM and WDM. In terms of development efficiency, compared with experienced developers, the agent is two orders of magnitude more efficient. The application of this agent will bring about a major revolution in numerical-simulation-based cosmology research. Hundreds or thousands of models that previously could not be tested by simulations will become testable, and the most time- and expertise-consuming part of this field has been overcome. We believe that the human–AI collaboration method developed in this study can be extended to a broader range of research fields and may bring about a profound transformation of research paradigms.

        Speaker: Jiajun Zhang (Shanghai Astronomical Observatory)
      • 17:00
        Cosmological studies with cosmic microwave background and radio observations 30m

        Observations of the cosmic microwave background (CMB) and radio wavelengths can probe multiple evolutionary stages spanning the early to late Universe, which feature large-scale structures and long-timescale processes. These observations are therefore of fundamental importance for investigating core physical problems concerning dark matter, dark energy, and gravitational waves. Future CMB polarization observations, with unprecedented sensitivity and resolution, may detect more exotic early- and late-Universe polarization signals, posing potential challenges to the standard cosmological model. The CMB formed when photons decoupled from the photon-baryon plasma during hydrogen recombination, as free electrons were captured to form neutral atoms. Similarly, the redshifted 21 cm line of neutral hydrogen can also trace dark-matter-dominated large-scale structures across a wide range of redshifts and spatial scales. This talk will present the scientific objectives, recent research progress, and future plans for cosmological studies centered on the cosmic microwave background (CMB) and neutral hydrogen.

        Speaker: Prof. Chang Feng (University of Science and Technology of China)
      • 17:30
        Luminal scalar-tensor theories via couplings to photons 30m

        The detection of GW170817 and its electromagnetic counterpart placed a stringent bound on the difference between the speeds of gravitational waves and light, severely restricting viable scalar-tensor models of dark energy. In particular, large parts of Horndeski and beyond Horndeski theories appeared to be ruled out as a description of late-time cosmic acceleration. In this talk we revisit this conclusion. We argue that the constraint concerns the relative propagation of gravitons and photons, so a consistent treatment must include possible interactions between the dark energy scalar and the electromagnetic sector. Using Kaluza–Klein reductions of higher-dimensional scalar-tensor theories as a guiding principle, we construct classes of self-consistent scalar–vector–tensor theories within the DHOST framework in which gravitational waves and light propagate with equal speeds on cosmological backgrounds. We discuss which of these couplings cannot be removed by conformal or disformal field redefinitions, the fate of gravitational wave decay into dark energy, and the implications for screening mechanisms and observational tests.

        Speaker: Arina Shtennikova (INR RAS & ITMP MSU)
    • 14:00 → 18:00
      Parallel-Gravity: Parallel-Gravitation
      • 14:00
        Quantum geometry effects in quantum field theory: Hamiltonian constraint generates gravity-matter entanglement in spherically symmetric loop quantum gravity 30m

        In this work, we address a foundational challenge in quantum field theory on curved spacetime by developing a consistent framework in spherically symmetric loop quantum gravity. We introduce a methodology for defining meaningful superpositions of quantum geometry and matter states near the semiclassical apparent horizon. This is achieved by identifying a restricted subspace of the gravitational phase space, which ensures unitary equivalence among Fock representations of a scalar field across different quantum geometries. Within the resulting well-defined state space, we derive weak solutions to the quantum Hamiltonian constraint of general relativity near the semiclassical apparent horizon. Furthermore, we generalize the Hartle-Hawking vacuum state to this quantum geometric framework. The resulting state exhibits the inherent entanglement between geometry and matter, which arises from the quantum Hamiltonian constraint of general relativity. This work establishes a principled framework for studying geometry-matter entanglement and offers new insights into the quantum foundations of the black hole information paradox.

        Speaker: Gaoping Long (Jinan University)
      • 14:30
        Static Vacuum Geometry Determines Gravitational Collapse and Cosmology 30m

        Beyond general relativity, regular black-hole geometries and modified cosmologies are often constructed independently, raising the question of whether black holes, gravitational collapse, and cosmology can still arise as different regimes of a common gravitational dynamics. We answer this question by showing that, within the covariant spherically symmetric effective Hamiltonian framework, the dynamics of gravity coupled to irrotational dust can be determined directly from a prescribed static vacuum family, although the Hamiltonian reconstruction of that family is not unique. Requiring the resulting dust dynamics to admit an FLRW sector further yields a necessary and sufficient restriction on the static vacuum family and determines the corresponding modified Friedmann equation. Thus, static vacuum geometry determines the collapse dynamics, while cosmological homogeneity feeds back to select the admissible static geometries. This generality may be rooted in the combined roles of general covariance and Birkhoff's theorem in the underlying theory.

        Speaker: cong zhang (Beijing Normal University)
      • 15:00
        Quantum Damping of Cosmological Shear: A New Prediction from Loop Quantum Cosmologies 30m

        We study the dynamics of the Bianchi I universe in modified loop quantum cosmology (mLQC-I) and uncover a robust mechanism for isotropization: the shear is dynamically suppressed after the bounce and decays rapidly in the quantum postbounce regime, independently of the equation of state of standard matter sources. This naturally drives the Universe toward a homogeneous and isotropic expanding phase without fine-tuning. Our results show that mLQC-I provides a new quantum-gravitational mechanism for suppressing anisotropies, absent in other bounce models.

        Speaker: Wencong Gan (Jiangxi Normal University)
      • 15:30
        A loop quantum gravity inspired effective action in spherically symmetric background and its applications 30m

        Developing covariant effective descriptions of quantum-corrected black holes is an important challenge in loop quantum gravity (LQG). In this talk, I will present an LQG-inspired effective action in spherical symmetry that admits the quantum Oppenheimer–Snyder (q-OS) black hole as a vacuum solution. Starting from a two-dimensional dilaton gravity framework obtained by integrating out the angular degrees of freedom, the construction introduces an auxiliary constraint sector that promotes the mass parameter to a spacetime scalar and enforces its constancy on shell, without introducing local propagating degrees of freedom. Using the covariant phase space formalism, I will discuss the associated Hamiltonian charges and black hole thermodynamics. The Wald entropy contains the classical area term together with a logarithmic correction, while the auxiliary sector contributes a boundary term essential for a consistent first law. I will then present a generalized Birkhoff theorem showing that the vacuum sector admits a two-parameter family of locally static solutions. The additional integration constant is not fixed by asymptotic flatness, and setting it to zero selects the q-OS branch. Its variation raises an integrability issue for the thermodynamic phase space. These results provide a covariant framework for investigating quantum-corrected black hole dynamics, entropy, and the physical conditions required to select particular vacuum solutions.

        Speaker: Dr hongwei Tan (Hunan Institute of Technology)
      • 16:00
        Break 30m
      • 16:30
        Regular ultracompact objects as polymerized vacuum solutions 30m
        Speaker: Dr Ioannis Soranidis (Westlake University)
      • 17:00
        Scalarization of Bardeen spacetime 30m

        We study the scalarization of the entire Bardeen spacetime which is constructed from a nonlinear magnetic monopole. For the pure Bardeen model, it is well known that there exist not only the general horizonless, nonsingular Bardeen spacetime solutions but also regular black hole (BH) solutions. When considering the Bardeen model coupled to a scalar field, we find that under the premise of solving throughout the entire spacetime (i.e., the radial coordinate $r\in[0,\infty)$ ), there are two scenarios: one is the trivial pure Bardeen solution with a vanishing scalar field, and the other is a horizonless, nonsingular scalarized Bardeen spacetime (SBS) solution. Depending on the value of the magnetic charge $q$, these non-trivial solutions can be further divided into two categories: (1) When the magnetic charge $q$ is below a certain critical value $q_c$ and the scalarization parameter $a$ approaches the scalarization threshold $a_t$ from above (i.e., $a\to a_t^+$), the scalar field vanishes, and the spacetime reduces to the horizonless, nonsingular pure Bardeen spacetime. This behavior indicates that this solution exhibits the general spontaneous" scalarization phenomenon. (2) When $q \geq q_c$, in the limit $a \to a_t^+$, the scalar field is non-vanishing and the SBS approaches afrozen" SBS. Considering the importance of photon orbits in astronomical observations, we analyze the trajectories of photons around SBSs by analyzing null geodesics.

        Speaker: Long-Xing Huang (Lanzhou University)
      • 17:30
        The complex conformal Kähler structure of type-D spacetimes 30m

        This is a work about the complex conformal Kähler structure and the related duality symmetry of Plebański-Demiański class, a kind of type-D spacetime. We reviewed the complex metric and complex Kähler structure of complex spacetimes, which has the complex valued metric and almost complex structure as well as the related potential function. We find a SO(2, C) duality transformation of Kerr-Taub-NUT class which maps Kerr metric into Taub-NUT metric continuously. What's more, using the results above, we get a Monge-Ampère equation which is equivalent to the vacuum Einstein equations and the solution of it contains the whole Plebański-Demiański Class, and theoretically the type-D spacetimes. Then we use toric reduction to obtain some moment polytopes and then use this one can classify different type-D solutions based on the complex conformal Kähler structure. We also find a complex Monge-Ampère equation and one can obtain the whold type-D by solving it. This is a joint work with Prof. Lars Andersson.

        Speaker: Mr Haoran Xu (HIAS)
    • 18:00 → 20:00
      Banquet 2h
  • Sunday, 8 November
    • 08:30 → 12:00
      Plenary Session
      • 08:30
        Modeling extreme mass-ratio inspirals in astrophysical environments 45m
        Speaker: Prof. Huan Yang (Tsinghua University)
      • 09:15
        Relic Gravitational Waves from Cosmic Domain Walls 45m
        Speaker: Prof. Dmitry Gorbunov (Institute for Nuclear Research of the Russian Academy of Sciences)
      • 10:00
        Break 30m
      • 10:30
        Gravity/thermodynamics correspondence via black hole shadows 45m
        Speaker: Prof. Shao-Wen Wei (Lanzhou University)
      • 11:15
        Conversations between Extreme Physical Scales 45m
        Speaker: Prof. Lerothodi Leonard Leeuw (University of Pretoria)
    • 12:00 → 14:00
      Lunch 2h
    • 14:00 → 18:00
      Parallel-Astrophysics
      • 14:00
        A new window for astrophysics from the lunar orbit 30m

        I shall present the Discovering Sky at the Longest wavelength (DSL) mission, also known as the Hongmeng mission in Chinese, which aims to unveil the sky at this low frequency band by using an array of microsatellites flying in formation on an orbit around the Moon. The mission will make highly precise 21cm global spectrum measurement in the 0.1-30 MHz band and in the 30-120 MHz band, without being hindered by ionospheric distortion, radio frequence interferences, or ground reflections. This will reveal the cosmic evolution history from the dark ages to cosmic dawn. The satellite array will also make high resolution full sky maps in the 0.1-30 MHz band, which will provide new observational clues to the study of the Galactic interstellar medium, extragalactic radio sources, and solar and planetary activities. Observation in this new window may also reveal unknown new objects or phenomena. The DSL mission science team welcomes the participation of the international science community.

        Speaker: Prof. Xuelei Chen
      • 14:30
        RadioSkySim: A Flexible and Scalable Python Framework for Radio-Astronomical Sky Simulation 30m

        RadioSkySim: A Flexible and Scalable Python Framework for Radio-Astronomical Sky Simulation

        RadioSkySim is a Python-based sky simulation framework developed within the BINGO Collaboration to support the modeling, analysis, and validation of radio-astronomical observations. Designed with an emphasis on modularity, extensibility, and computational efficiency, it provides a flexible environment for generating realistic simulated observations while maintaining a clear separation between scientific models and computational infrastructure.

        The framework implements a library of instrumental beams with polarization support, astronomical radio sources, local sources, and GNSS satellites, enabling the construction of complex and configurable observing scenarios. These components can be combined to generate time-ordered data (TOD), currently stored in NetCDF format, and to support subsequent map-making and analysis workflows.

        RadioSkySim adopts a hexagonal architecture that facilitates the integration of different computational backends and scientific models without coupling them to the core simulation logic. Its architecture also incorporates caching and database persistence mechanisms, together with multi-core execution capabilities, allowing simulations to be efficiently reused, scaled, and integrated into larger data-processing pipelines.

        Beyond its current capabilities, the framework was designed as a foundation for more demanding simulation scenarios, including GPU-accelerated computation, additional classes of sky and foreground components, and increasingly sophisticated instrument models. This approach aims to provide the BINGO Collaboration with a sustainable simulation infrastructure capable of supporting both experimental development and scientific analysis.

        In this talk, we present the architecture and main capabilities of RadioSkySim, discuss its current implementation and use cases, and illustrate how its design enables the progressive incorporation of new physical models, instrumental effects, and computational strategies.

        Speaker: Prof. Luciano Barosi (Universidade Federal de Campina Grande)
      • 15:00
        Cosmological forecast from bispectrum of 21cm intensity mapping 30m
        Speaker: Prof. Yu Sang (Yangzhou University)
      • 15:30
        A Designer’s Guide to Lunar Far-Side Interferometer Array: Power Spectrum Measurement and Cosmological Information in the Dark Ages 30m

        The 21-cm signal from the cosmic Dark Ages is a powerful probe of cosmology and
        inflation, but its science potential depends critically on the design of the lunar
        far-side interferometer that will observe it. We derive closed-form relations
        connecting the array design to the two goals this epoch offers: measuring a chosen
        small scale, and extracting the largest possible cosmological information from the
        survey as a whole. These relations provide a quantitative prescription of resources required to reach a stated detection threshold at a tunable scale of interest and show that the optimal configuration for the power spectrum at that scale is to split the collecting area among multiple stations. For fixed resources, splitting a single array into two or three stations
        can raise S/N at $k_\perp = 1\,\mathrm{Mpc}^{-1}$ by factors of about 10 and 16, reaching two orders of magnitude at smaller scales. For the purpose of cosmological parameter constraints, we derive where the cosmological information accessible to a lunar array resides, in redshift and in transverse wavenumber, and find that thermal noise erodes the often-quoted $10^{12}$ modes to an effective budget of order $10^{4}$, half of which accumulates below $z \approx 36$. As a demonstration, we forecast $\sigma(\alpha_s) = 0.034$ for the running of the spectral index assuming a near-term array configuration, illustrating both the prospects and the limitations implied by these relations.

        Speaker: Dr Yuewei Wen (National Astronomical Observatories of China, Chinese Academy of Sciences)
      • 16:00
        Break 30m
      • 16:30
        Measuring Geometric Distances Using Interferometry and Reverberation Mapping of Broad-line Regions 30m

        The geometric distances of active galactic nuclei (AGNs) are challenging to measure because of their exceptionally compact structure, yet vast cosmic distances. A combination of spectroastrometry and reverberation mapping (SARM) of broad-line regions (BLRs) constitutes a novel means to probe the geometric distance of AGNs, which has recently become practically feasible owing to successful interferometric observations with the Very Large Telescope Interferometer/GRAVITY. Here, we perform SARM analysis of four nearby quasars: Mrk 509, PDS 456, 3C 273, and NGC 3783. Results for the former two are reported for the first time, and the latter two are revisited using our improved BLR dynamical modeling that includes the radial-dependent responsivity of BLRs. This allows us to self-consistently account for the emissivity weighting of the BLR in spectroastrometry and responsivity weighting in reverberation mapping. We obtain angular-diameter distances of the four quasars, from which we derive a Hubble constant of H0=69(−10 +12)km/s/Mpc . Although this constitutes a large uncertainty for a measurement of H0, it is anticipated that the precision will improve to a competitive level once a greater number of AGNs are accessible following the upgrade of GRAVITY in the near future.

        Speaker: Prof. Yan-Rong Li (Institute of High Energy Physics)
      • 17:00
        Too Quiet to Be Ordinary: Little Red Dots 30m

        JWST's little red dots (LRDs) are unexpectedly non-variable. We present a semi-analytic framework for variability in super-Eddington slim disks with winds, combining photon trapping, photospheric averaging, and diffusion filtering, calibrated on ordinary quasars. Forward-modeling the TWINKLE non-detections of 18 LRDs, we derive a lower limit ṁ ≳ 60 (95% confidence) for 10⁷ M⊙ black holes, excluding sub-Eddington interpretations, and predict mass-segregated variability and suppressed X-ray variability that are testable with future observatories.

        Speaker: Dr INDU KALPA DIHINGIA (Ningbo University)
      • 17:30
        [online] Revisiting PBH Accretion, Evaporation and Their Cosmological Consequences 30m

        Primordial black holes (PBHs) provide a unique probe of the early Universe. Their cosmological evolution is governed by the competition between mass accretion and Hawking evaporation. In this paper we look into the details impact of accretion. Most of the earlier analysis relied on non-relativistic accretion models. In this work, we reinvestigate this in a fully relativistic framework for Kerr PBHs in the radiation-dominated era. We derive relativistic accretion rate and compute spin-dependent efficiency $\lambda_{\rm Kerr}(a_*)$. Using this result, we construct coupled evolution equations for the PBH mass and spin that include both relativistic accretion and spin-dependent evaporation. Our analysis shows that relativistic accretion significantly increases PBH masses and consequently suppresses their spins, causing all PBHs to become effectively Schwarzschild well before evaporation. These effects strengthen the Big Bang Nucleosynthesis (BBN) bound on the initial PBH mass by a factor of $\sim 4-5,$ reduce the mass required for survival to the present epoch to $\sim 2.7 \times 10^{14} \rm g,$ and shift the viable particle like DM parameter space. Notably the early accretion induced spin-down effect further washes out the well known high-frequency, spin-induced feature in the high frequency stochastic gravitational-wave background, modifying predictions for future detectors.

        Speaker: Mr JITUMANI KALITA (Indian Institute of Technology Guwahati)
    • 14:00 → 18:00
      Parallel-Cosmology
      • 14:00
        From Ultralight to Macroscopic Dark Matter: A Window into the Dark Sector with Gravitational Waves 30m

        Dark matter may leave observable signatures in gravitational-wave detectors through a remarkably broad range of physical mechanisms. In this talk, I will discuss recent searches using data from the fourth observing run of the LIGO–Virgo–KAGRA detector network. First, I will present a direct search for ultralight dark matter, in which coherently oscillating scalar, vector, and tensor fields can produce characteristic signals in gravitational-wave interferometers. I will then discuss searches for gravitational waves from inspiraling planetary-mass and asteroid-mass ultra-compact objects, which could be primordial black holes. Finally, I will discuss how related continuous-wave searches can probe ultralight bosons through gravitational radiation from boson clouds surrounding rotating black holes. Together, these searches illustrate how gravitational-wave detectors can function not only as observatories of conventional astrophysical sources, but also as sensitive experiments for exploring the nature of dark matter.

        Speaker: Andrew Miller (ICTP - AP / University Chinese Academy of Sciences)
      • 14:30
        Mapping the ALPs: A Naturalness Map for Axions and ALPs 30m

        The axion solution to the strong CP problem is only as robust as the Peccei-Quinn symmetry it relies on, and quantum gravity is expected to break it. We quantify the resulting axion quality problem using principled measures of fine-tuning, and show that the cost is severe. For the QCD axion to account for the observed dark matter, Planck-suppressed symmetry-breaking operators must be absent up to mass dimension $d \ge 12$; the naturalness penalty for failing to realize this protection can exceed a Bayes factor of $10^{10}$. Extending the analysis to generic axion-like particles, we map the axion mass-decay constant plane by the degree of UV protection required, and find that large portions of the sensitivity reach of laboratory experiments are already fine-tuned at the part-per-million level or worse. We argue that quality, not mass, is the central naturalness question for the axion program.

        Speaker: Andrew Fowlie (XJTLU)
      • 15:00
        Audible curvaton: modulated phase transition as the origin of large-scale curvature perturbations and gravitational wave anisotropies 30m

        I will discuss a new mechanism for generating primordial large-scale curvature perturbations and gravitational wave (GW) anisotropies via a first-order phase transition modulated by a light spectator field. The spectator acquires fluctuations during inflation, which come into play at a post-inflation phase transition by modulating the bubble nucleation rate. Such a modulation induces spatial variations in the transition time and characteristic bubble scale, producing the observed amplitude of primordial curvature perturbations together with sizable, correlated GW anisotropies. We identify a benchmark with GW anisotropies potentially observable by future space-based detectors and local primordial non-Gaussianity within reach of next-generation large-scale-structure surveys.

        Speaker: Wenyuan Ai (Shanghai Jiao Tong University)
      • 15:30
        Scalar Induced Gravitational Waves Probing Phase Transitions in the Standard Model and Beyond 30m

        Scalar induced gravitational waves (SIGW) are a powerful probe of dynamics in the Standard Model and BSM models in the early Universe. In particular, the equation of state and sound speed have a non-trivial time dependence during phase transitions, which will impact the spectrum of induced GWs. In this talk, I will present a detailed calculation of SIGW in a general time-dependent thermal bath. We derive general initial conditions for metric perturbations in the superhorizon limit, and explain special features of the GW spectrum associated with phase transitions. I will show that the QCD crossover can leave observable features in the Pulsar Timing Array window, while BSM phase transitions, such as in composite Higgs models, can be probed by LISA, Taiji and TianQin.

        Speaker: Peizhi Du
      • 16:00
        Break 30m
      • 16:30
        Tracing out massive fields in cosmology 30m

        Cosmological correlators are calculated through the in-in formalism in (quasi-)de Sitter background. Their effective description is best represented by a reduced density matrix. In this talk, I will first review the differences between the usual EFT used in scattering amplitude calculations and the Schwinger-Keldysh EFT for correlators. I will then discuss the reduced density matrix for a light field at finite time, obtained by tracing out a massive field in a quasi-single-field model with non-linear couplings. The trace generates branch-mixing terms which are generally present in the Schwinger-Keldysh formalism. Explicit calculations of the effective description and the bispectrum will be shown for a conformally coupled massive field. I will then discuss how a local effective field theory is obtained through a large mass expansion of the exact non-local effective description. Finally, I will study the symmetry and Schwinger-Keldysh constraints on the reduced density matrix.

        Speaker: Guanhao Sun (Chongqing University)
      • 17:00
        How Does a Thermal Medium Affect Primordial Gravitational Waves? 30m

        A thermal medium modifies the propagation of gauge fields, producing collective excitations with a plasmon gap. Does it affect primordial gravitational waves in the same way? For gravity, the thermal soft scale coincides with the Hubble rate, making cosmic expansion essential to answering this question. In this talk, I compute the linear response of thermal radiation, modeled by a conformal scalar, to metric perturbations on a spatially flat FLRW background. The calculation retains both retarded and contact contributions and satisfies the diffeomorphism Ward identities. Although the adiabatic dispersion relation exhibits a gap, $\omega_p^2=8\mathcal H^2/5$, with $\mathcal H$ the conformal Hubble rate, superhorizon tensor modes remain conserved when the initial-time boundary of the retarded response is retained. The real-time evolution reproduces Weinberg’s gravitational-wave damping, with amplitude suppression accumulating around horizon reentry. I also explain how the superhorizon growth found in our earlier analyses arose from discarding the response history and adopting a state prescription incompatible with the Ward identities. These results clarify how a thermal collective gap coexists with conserved primordial perturbations and why cosmological evolution requires a real-time treatment.

        Speaker: Atsuhisa Ota (Chongqing University)
      • 17:30
        Revisiting Primordial Black Hole Formation from Primordial Gravitational Waves 30m

        Primordial gravitational waves generate radiation density perturbations at second order, providing a possible connection between small-scale tensor power and primordial black hole (PBH) formation. In this talk, we revisit this connection using a finite-time semianalytic solution for arbitrary source momenta. The solution retains the regular homogeneous contribution fixed by the initial spatial curvature and separates it from the subsequent tensor source. For Gaussian primordial tensors, we calculate the probability distribution of the quadratic density contrast smoothed at horizon reentry and compare the resulting PBH abundance estimates with a Gaussian density approximation. We examine how the positive density tail depends on the specified initial geometry and illustrate the effects of finite-width tensor spectra. We also assess perturbative validity by evaluating the tensor strength in regions exceeding the adopted density threshold. In the cases studied, the inferred tensor powers and the conditional mean squared tensor amplitudes are of order unity. These results clarify the assumptions underlying PBH bounds on primordial gravitational waves and motivate nonlinear evolution with a collapse criterion calibrated for tensor-induced density profiles and shear.

        Speaker: Dr Peng Zhi-Zhang (Yangtze University)
    • 14:00 → 18:00
      Parallel-Gravity: Parallel-Gravitation
      • 14:00
        Learning quark-gluon plasma properties holographically with neural ODEs 30m

        We use neural ODEs and state-of-the-art lattice QCD thermodynamics to calibrate a holographic Einstein-Maxwell-Dilaton model with Gauss-Bonnet corrections. The model quantitatively reproduces the equation of state at zero and finite baryon chemical potential and predicts the phase structure in the T-mu_B plane, a temperature-dependent ratio of shear viscosity over entropy, and a peaked ratio of bulk viscosity over entropy, while remaining consistent with thermodynamic constraints.

        Speaker: Prof. Song He (Ningbo University)
      • 14:30
        Timelike Entanglement First Law and Linearized Field Equations in Higher Curvature Gravity 30m

        We investigate the timelike entanglement first law in holographic conformal field theories whose bulk dual is Lovelock gravity. Using the double Wick rotation formulation of timelike entanglement entropy together with the Jacobson-Myers entropy functional, we compute the linear variation of holographic timelike entanglement entropy for hyperbolic subregions. For cubic Lovelock gravity, we explicitly show that a single, universal multiplicative renormalization factor governs how higher curvature interactions enter the variations of both the entropy and the modular Hamiltonian, leading to $\Delta S=\Delta\langle H\rangle$ for low-energy thermal excitations. We then extend the analysis to Lovelock gravity of arbitrary order around the anti-de Sitter spacetime in the Fefferman-Graham gauge. For normalizable perturbations, the variation of the Jacobson-Myers functional reduces to the Einstein gravity's result multiplied by the same coupling-dependent factor that renormalizes the effective Newtonian constant in the linearized field equations of Lovelock gravity. We further show that the boundary contribution vanishes in the conformal limit for the class of perturbations considered. Consequently, the timelike entanglement first law is equivalent to the linearized field equations of Lovelock gravity about the maximally symmetric background.

        Speaker: Prof. Jia-Rui Sun (Sun Yat-Sen University)
      • 15:00
        Nash Equilibrium from Quantum-Field Entanglement 30m

        Entanglement harvesting transfers quantum field correlations to localized probes, yet whether these correlations can alter stable strategic behavior has remained unclear. We formulate a quantum-input game in which two Unruh–DeWitt detectors harvest vacuum entanglement from a free massless scalar field in $(3+1)$-dimensional Minkowski spacetime. A referee converts this state into payoffs using independent question qubits and phase-calibrated local Bell measurements. To leading perturbative order, the mean reward is proportional to the signed entanglement margin $\sqrt{\mathcal H^2+\mathcal Q^2}-\mathcal P$, where $\mathcal H$ is the Hadamard correlation contribution, $\mathcal Q$ is the Pauli--Jordan causal contribution, and $\mathcal P$ is the local excitation noise. Away from payoff degeneracies, allowing each player to exit or to choose an early or late interaction yields $1+2n_+$ trembling-hand perfect equilibria, where $n_+$ counts the positive-reward timing equilibria. For one fixed protocol, five analytically certified settings realize the sequence $7\to3\to1\to7\to1$. They represent the spacelike region, the first commutator lobe, central carrier cancellation, the second lobe, and the post-wavefront Huygens regime. Thus, within this fixed quantum-input verification protocol, distinct field-correlation regimes generate different stable strategic structures.

        Speaker: Prof. Hao Xu (Yangzhou University)
      • 15:30
        Semileptonic $B\to D$ and $B_s\to D_S$ decays in the AdS/QCD Softwall model 30m

        We present a holographic calculation of the semileptonic decays $B\to D$ and $B_s\to D_s$ within the AdS/QCD Softwall Model. Heavy-light mesons are described by normalizable bulk modes, while the flavor-changing current $J_\text{EW}^\mu=\bar{c}\,\gamma^\mu\,b$ is associated with a massless bulk vector field, motivated by the UV scaling dimension $\Delta=3$ of the QCD current. An effective bulk interaction yields the overlap integral from which we extract the holographic Isgur-Wise function $\xi(\omega)$, and the vector $f_+(q^2)$ and scalar $f_0(q^2)$ form factors. We also evaluate the Lepton Flavor Universality Ratios $R(D)$ and $R(D_s)$, comparing our predictions with lattice QCD and available experimental data. Finally, we discuss the limitations of the leading-order holographic description.

        Speaker: Prof. Miguel Angel Martin Contreras (University of South China)
      • 16:00
        Break 30m
      • 16:30
        Diagonally gauged anomaly-free 6D supergravities and their vacua 30m

        We describe a bounded search for local and global anomaly-free six-dimensional $(1,0)$ models with tensor number $T=1$ and gauge group containing a diagonal abelian factor $U(1)_{R+}$. The abelian factor is the diagonal combination of the usual gauged $U(1)_R$ and a $U(1)\subset Sp(n_H)$ acting on hypermultiplets. We have searched for locally and globally anomaly-free $G_1\times U(1)_{R+}$ and $G_1\times G_2\times U(1)_{R+}$ models, subject to restrictions on the ranks of the simple factors and on the maximal charges carried by matter. We find that, unlike the case of $U(1)_R$ gauged models which are relatively rare, the diagonally gauged ones offer a rich landscape. We also study the 6D vacua of these models and find that they admit supersymmetric 6D Minkowski vacua, for which the diagonal nature of the R-symmetry gauging is necessary.

        Speaker: Yi Pang (Tianjin University)
      • 17:00
        Can higher derivatives resolve the black-hole singularity? 30m

        Higher-derivative and nonlocal gravity models arise in various approaches to quantum gravity, either as candidates for renormalizable theories of gravity or as effective low-energy descriptions. In this talk, we present several recent results on classical solutions in higher-derivative gravity, focusing on the possibility of resolving the black-hole singularity present in solutions of general relativity and quadratic gravity. We discuss the first local classification of static, spherically symmetric exact solutions in generic six-derivative gravity and in a quasi-local extension of Einstein-Weyl gravity. Although only regular cores are found in both cases, we argue that more complicated singular solutions might still exist and discuss the possibility of having regular black holes in these models.
        [Based on: JCAP 07, 080 (2026); PRD 113, L041502 (2026); PRD 112, 024051 (2025); PRD 110, 104056 (2024).]

        Speaker: Breno Loureiro Giacchini (Charles University)
      • 17:30
        Quantum Gravity Corrections: From Background Dynamics to Cosmological Perturbations 30m

        Quantum-gravity models often provide effective background dynamics, while cosmological observables depend on the dynamics of inhomogeneous perturbations. I will discuss a Hamiltonian framework for bridging this gap. Requiring consistent local evolution strongly constrains how a modified homogeneous or symmetric dynamics can be completed into a spatial theory. The resulting Hamiltonian determines not only the cosmological background but also its scalar and tensor response.
        I will discuss how relational scale setting and non-perturbative renormalization can provide quantum input for this effective dynamics, and how the same Hamiltonian framework connects it to cosmological perturbations and correlation functions.

        Speaker: Hongguang Liu (Westlake University)
    • 18:00 → 20:00
      Dinner 2h
  • Monday, 9 November
    • 08:00 → 12:00
      Parallel-Astrophysics
      • 08:30
        Shadow of rotating black hole surrounded by dark matter 30m

        暗物质（DM）是宇宙的基本组成成分，因此有必要研究其对黑洞（BH）阴影的影响，尤其是事件视界望远镜（EHT）观测所证实的旋转黑洞。本文利用 Newman–Janis 算法（NJA），将暗物质环绕的施瓦西黑洞解推广为轴对称的克尔黑洞解，并研究其事件视界与能层结构。通过分析零测地线，我们考察了暗物质质量（(\Delta M)）对黑洞阴影半径、形变及相关能量发射率的影响。结果表明，当暗物质质量低于某一临界值时，其影响可以忽略；一旦超过该阈值，黑洞的各类结构均显著扩张。此外，即使黑洞具有较高自旋，暗物质仍有助于其阴影保持近圆形轮廓。较大暗物质质量引起的显著结构扩张可能超出当前观测约束。这表明，为与天体物理观测保持一致，黑洞紧邻区域内应不存在暗物质，或其中的局域暗物质质量必须低于该临界值。

        Speaker: Haiyuan Feng (Shanxi Normal University)
      • 09:00
        Torsion-Induced Four-Fermion Interactions in Gravitational Collapse 30m

        The intrinsic spin of fermions generates torsion in spacetime. This gives rise to a parity-violating, nonuniversal four-fermion interaction, which is expected to become significant in dense matter, such as in early-universe cosmology or in neutron stars. We calculate the effect of the interaction term in a gravitationally collapsing gas of fermions with an isotropic spin distribution. We use the Raychaudhuri equation and the focussing condition for congruences for a collapsing distribution of multiple species of fermions, ignoring other interactions. We establish that a repulsive contribution can arise depending on how torsion couples with different chiralities. The effect of the interaction starts to dominate as density increases, accelerating or decelerating the collapse depending on the torsional coupling constants of different fermions.

        Based on : S. G. Choudhury, S. K. Maity, and A. Lahiri. Torsional four-fermion interaction and the Raychaudhuri equation. Eur. Phys. J. C, 84(12):1304, (2024).

        Speaker: Mr Sagar Kumar Maity (S. N. Bose National Center for Basic Sciences)
      • 09:30
        [online] Static black hole surrounded by dark matter and cloud of strings 30m

        We investigate a Schwarzschild-like black hole embedded in a combined environment consisting of a Dehnen-type dark matter halo and a cloud of strings. We first construct the corresponding composite spacetime metric and examine its geometric properties, including the horizon structure, curvature invariants, and the validity of the classical energy conditions. Subsequently, we explore the geodesic dynamics of test particles by analyzing the effective potential, circular orbits, and the innermost stable circular orbit (ISCO). We also study the optical appearance of the black hole by computing its shadow and assessing how the surrounding dark sector components modify its observable features. Our results elucidate the influence of dark matter distributions and string clouds on black hole geometry and dynamics, highlighting characteristic signatures that could serve as potential observational probes with current and future astrophysical facilities.

        Speaker: Ahmad Albadawi (Al-Hussien Bin Talal university)
      • 10:00
        Break 30m
      • 10:30
        [online] Meissner Effect and Kerr/CFT Holography of Extremal Kerr–Bertotti–Robinson Black Holes 30m

        The Kerr–Bertotti–Robinson (Kerr–BR) spacetime is a recently constructed exact Einstein–Maxwell solution describing a rotating black hole immersed in a homogeneous Bertotti–Robinson electromagnetic universe. Unlike the familiar Melvin-type magnetized Kerr families, its asymptotics are AdS₂ × S², the external field explicitly deforms the horizon and extremality condition, and its Maxwell and Weyl principal null directions are misaligned. In this talk I examine two complementary near-horizon phenomena of the extremal Kerr–BR black hole and show that both are governed by the same Kerr/CFT data. First, I establish the Meissner effect in a manifestly gauge-invariant way: the horizon-tangent field strength vanishes, so the external magnetic flux is fully expelled, while the residual gauge coefficient survives only as a local Wilson-line term. Second, I derive the near-horizon Breitenlohner–Freedman instability criterion for a charged scalar probe, expressed through two gauge-invariant combinations — the shifted fibre momentum and the effective Kaluza–Klein electric coupling. Both the Meissner expulsion and the BF threshold turn out to be controlled by the twist parameter and gauge coefficient that enter the holographic dictionary, revealing them as two probes of a single extremal throat whose structure is fixed by the external field.

        Speaker: Dr Siahaan Haryanto Mangaratua (Parahyangan Catholic University)
      • 11:00
        Neutron stars more compact than black holes 30m
        Speaker: Dr Shonglong Li
      • 11:30
        A Neutron Star Hidden Inside a Black Hole 30m

        We investigate dark matter admixed neutron stars in which the neutron star coexists with an anisotropic dark matter halo described by the Einasto density profile, a model recently shown to produce regular, singularity-free black hole solutions~[Phys. Rev. D \textbf{113}, 043011 (2026)].
        Solving the modified Tolman--Oppenheimer--Volkoff equations with two different equations of state (BSk19 and SLy4), we find that the dark matter halo significantly alters the neutron star structure.
        Furthermore, for a specific range of halo parameters, $g_{rr}^{-1}$ changes sign outside the stellar surface, forming an event horizon with the neutron star persisting as a regular configuration inside it--- ``neutron stars in black holes''.
        This configuration appears in both equations of state and does not depend on a specific choice of the equation of state.
        The discovery of this configuration provides a new perspective and a concrete computable instance for the study of what lies inside a black hole.

        Speaker: Chen Tan (Lanzhou University)
    • 08:00 → 12:00
      Parallel-Cosmology
      • 08:30
        The Generation and Detection of Chiral Gravitational Wave Background 30m

        Chiral gravitational wave backgrounds are predicted in many well-motivated mechanisms. We investigate the detection of Chiral GWBs using a network of detectors under arbitrary configurations. We also propose a dipole pulsar timing array, which demonstrates sensitivity to Chiral gravitational wave backgrounds from the nanohertz to microhertz regime.

        Speaker: Yun-Long Zhang (NAOC(National Astronomical Observatories, CAS))
      • 09:00
        A Template-Based Search for Large-Scale-Structure--Correlated Anisotropy in the Nanohertz Gravitational-Wave Background Using the Public NANOGrav 15-Year Data Set 30m

        Recent PTA analyses reporting evidence for a nanohertz common-spectrum process motivate targeted tests of whether any anisotropic component of the stochastic gravitational-wave background (SGWB) is correlated with the nearby large-scale structure (LSS), as anticipated for an astrophysical background dominated by supermassive black hole binaries. We present the first Bayesian PTA likelihood analysis that embeds an externally observed, full-sky galaxy-survey LSS template directly as an overlap-reduction-function (ORF) component. Using the 2MASS Photometric Redshift (2MPZ) galaxy catalog, we construct low-multipole LSS--correlated ORF templates in two redshift slices ($0 where $\epsilon_i$ quantifies the amplitude of an SGWB component whose angular correlations project onto the fixed 2MPZ LSS templates. Applying this framework to the NANOGrav 15-year dataset, we find no evidence for an LSS-correlated component: the inferred $\epsilon_i$ values are consistent with zero in both single-bin and two-bin analyses (e.g., $\epsilon_1=0.20^{+1.68}_{-1.66}$ and $\epsilon_2=-0.11^{+2.04}_{-1.83}$; 68\% credible intervals), and Bayes factors favor the isotropic Hellings--Downs hypothesis ($\mathcal{B}_{{\rm HD+LSS}_1,{\rm HD}}=0.40$, $\mathcal{B}_{{\rm HD+LSS}_2,{\rm HD}}=0.43$, $\mathcal{B}_{{\rm HD+LSS}_{1+2},{\rm HD}}=0.11$). We therefore place upper limits on any 2MPZ-traced, LSS-correlated contribution to the SGWB at $z<0.2$. More broadly, our framework provides a reproducible pathway for incorporating observed LSS information into PTA anisotropy searches and naturally motivates extensions to finer redshift tomography and next-generation PTA datasets.

        Speaker: Yun Fang (Institute of Fundamental Physics and Quantum Technology, Ningbo University)
      • 09:30
        [online] Kinematic Probes of Type-II Minimally Modified Gravity 30m

        We study the late-time expansion history of the Universe within the VCDM model, a Type-II MMG realization that preserves the successes of General Relativity while extending beyond constant vacuum energy through a minimal Hamiltonian modification, generating a time-dependent vacuum sector without introducing additional degrees of freedom. We investigate this framework within a cosmographic approach by employing a Pad\'e $P_{(2,1)}$ approximation for the Hubble parameter and luminosity distance, allowing the cosmographic parameters to be expressed directly in terms of the underlying VCDM model parameters and enabling a data-driven reconstruction of the expansion history. The model is constrained within a Bayesian framework using the MCMC technique, implemented via the affine-invariant ensemble sampler, with a joint analysis of cosmic chronometers, DESI BAO, and Type Ia supernova datasets (Union3, Pantheon+, and DESY5). We find that the model parameters are tightly constrained and consistent across different dataset combinations, with the jerk parameter remaining very close to its $\Lambda$CDM value, $j_0 \simeq 1$, indicating no significant deviation at the level of higher-order cosmography. Furthermore, the transition feature previously reported in VCDM is not observed within the Pad\'e $P_{(2,1)}$ cosmographic reconstruction, suggesting that it is not a robust requirement of current observational data but is sensitive to the choice of parametrization. Overall, our results indicate that the VCDM model effectively mimics $\Lambda$CDM at the background level when constrained through a cosmographic approach, underscoring the importance of model-independent reconstructions in assessing alternative cosmological scenarios.

        Speaker: Prof. Pradyumn Sahoo (Birla Institute of Technology and Science )
      • 10:00
        Break 30m
      • 10:30
        Inflation from Entropy: Inflationary Solutions in the Gravity from Entropy Framework 30m

        Gravity from entropy proposes quantum relative entropy between the spacetime metric and the metric induced by geometry and matter fields as the fundamental action for gravity. The resulting modified Einstein equations reduce to general relativity in the weak-coupling, low-curvature limit, while departing from it at high curvature. In this talk, I derive the Friedmann-equation analogues of GfE for a spatially flat FLRW universe and show that the vacuum equations admit inflationary solutions, with no inflaton field or added potential. This points to an entropic origin for inflation that avoids the need for a new scalar field. Assuming the standard relation between slow-roll parameters and CMB observables carries over to GfE, the theory predicts a viable primordial spectrum.

        Speaker: Udaykrishna Thattarampilly (Yangzhou University)
      • 11:00
        Resolving the Cosmological $^7$Li Abundance Anomaly via Baryon Emission from Evaporating Primordial Black Holes 30m

        Although the standard model of Big Bang nucleosynthesis successfully describes the formation of light elements, it faces a well-known challenge: the observed abundance of lithium-7 is approximately three times lower than the theoretically predicted value. This work proposes a mechanism to resolve this primordial lithium deficit through the emission of baryons by evaporating primordial black holes (PBHs). The lithium fraction can be efficiently reduced to the observed level via the transformation of $^7$Li through nucleon capture by lithium nuclei. This capture process produces $^8$Li or $^8$Be isotopes, which then rapidly decay into pairs of helium ($^4$He) nuclei. The analysis explores scenarios involving both "hot" and "cool" PBHs.

        Speaker: Prof. Elena Arbuzova (Dubna State University and Novosibirsk State University)
      • 11:30
        A Non Singular Cyclic Universe from Modified Gravity 30m

        The Big Bang singularity marks a fundamental breakdown of General Relativity, yet all proposed quantum gravitational remedies invoke microphysical assumptions beyond the observational reach. We show that a minimal, purely classical modification of the gravitational potential --- preserving the inverse-square law where tested, but free to depart at unmeasured scales --- is sufficient to produce a non-singular, cyclic universe. The resulting modified gravitational formulation leads to a cosmic evolution exhibiting a bounce at a finite minimum size, followed by a regime closely akin to the concordant $\Lambda$CDM model, and an eventual collapse to another bounce. Cosmic Chronometer, Supernovae type Ia, Baryon Acoustic Oscillation, Cosmic Microwave Background and Nucleosynthesis data constrain both the new length scales, implying a cycle period of ${\simeq}\,89\,\mathrm{Gyr}$, and this framework --- subsuming a broad class of bounce scenarios within a single testable model --- opens a direct route for distinguishing cyclic cosmologies from $\Lambda$CDM.

        Speaker: Dhiraj Kuniyal (Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India)
    • 08:00 → 12:00
      Parallel-Gravity: Parallel-Gravitation
      • 08:30
        Bianchi IX dynamics with a phantom field - a new type of BKL oscillations 30m

        We consider Bianchi IX dynamics of a Universe filled with a massless phantom field. Such an exotic matter source enables regimes impossible in vacuum or with a standard scalar field. In particular, two Kasner indices of BKL oscillations can be simultaneously negative, and the absolute value of a negative index can be large. We describe the consequences of these features and explain the nature of volume oscillations recently discovered in such a system by numerical methods.

        Speaker: Dr Alexey Toporensky (Sternberg Astronomical Institute)
      • 09:00
        Quasinormal Modes Decode Kasner Scaling inside Black Holes 30m

        Can the geometry hidden behind a black hole's event horizon be reconstructed from its exterior quasinormal-mode spectrum? In this talk, I will explore how high-overtone quasinormal modes encode information about black hole interiors. We show that distinct power-law corrections to the spectrum, obtained through angular-momentum and scalar-mass responses, allow the temporal and angular Kasner exponents to be extracted separately, without imposing the Kasner constraints. Using analytic monodromy methods and numerical calculations, we demonstrate this reconstruction in asymptotically flat black holes. In particular, we establish a four-dimensional Schwarzschild benchmark, where the predicted scaling behavior is confirmed numerically, and show that gravitational perturbations exhibit the same singularity-sensitive asymptotic structure. We further investigate dilatonic black holes, demonstrating that the reconstructed exponents track changes in the interior geometry. Complementary higher-dimensional and asymptotically AdS examples provide additional tests of the underlying mechanism. Our results establish a quantitative connection between exterior quasinormal-mode spectra and black hole interior geometry, opening a theoretical route toward probing otherwise inaccessible regions of spacetime.

        Speaker: Zi-Qing Xiao (ICTP-AP)
      • 09:30
        On the absence of inner horizons for anisotropic black holes 30m

        We establish a general no-inner horizon theorem for a wide class of static anisotropic black holes in Einstein gravity. As an application, we demonstrate that a large variety of black holes which possess homogeneous but anisotropic three-dimensional horizons can not have inner horizons. Our theorem is consistent with some previously known results, implying an underlying mechanism that certain kinds of spatial anisotropy can remove inner horizons. Consequently, anisotropic black holes generically develop spacelike singularities in their interiors, offering new insight into the interplay between anisotropy, strong cosmic censorship, and black hole interior structures.
        早期研究表明，黑洞内视界是动力学不稳定的，符合强宇宙监督假设。近年来的研究表明，非平庸的物质毛发会破坏黑洞的内视界；而报告人近期发现，各向异性标度行为也能破坏内视界。这类各向异性黑洞被广泛应用在全息对偶中。本报告将介绍相应的无内视界定理，以及一类具有Bianchi型视界的5维各向异性黑洞的内部结构的初步研究结果。

        Speaker: Mr Yuxuan Peng
      • 10:00
        Break 30m
      • 10:30
        Characteristic initial value problem and formation of black hole 30m
        Speaker: Prof. Xiaoning Wu (Institute of Mathematics, Academy of Mathematics and Systems Science)
      • 11:00
        Thermodynamics and chaotic orbits for semiclassical black hole with quantum anomaly correction 30m

        Black hole is an interesting physical object which is both a thermodynamical system and nest of chaos. In this talk, I will firstly introduce the conformal anomaly corrections on the black hole geometry in 4d spherical symmetric spacetime. After introducing the black hole solution, I will discuss the thermodynamics and chaotic properties of this black hole. We investigate the phase transition and critical phenomena of this anomaly corrected black hole and discover that anomaly can trigger the violation of Rushbrook scaling law at the critical point. This provides the first example of such scaling law violation in four dimensional spacetime. Moreover, we study the chaotic particle orbits around this black hole solution, we find that anomaly can enhance the chaotic features of the black hole which can also leave an imprint on the gravitational wave signals of the EMRI systems.

        Speaker: Yu-Sen An (Nanjing University of Aeronautics and Astronautics)
      • 11:30
        Thermodynamics of Kerr-Bertotti-Robinson black hole 30m
        Speaker: Dr Li Hu (Ningbo University)
    • 12:00 → 14:00
      Lunch 2h
    • 14:00 → 17:30
      Plenary Session
      • 14:00
        New type of SVT theory via disformal transformation 45m

        I will review known results on scalar-tensor theories, including their disformal transformations, stability and degeneracy.
        Next, will present recent results on scalar-vector-tensor theories with second order equations of motion.
        Finally, I will show a new class of degenerate SVT theories, that was obtained via disformal transformation.

        Speaker: Sergey Mironov (INR RAS, ITMP MSU, ITEP (NRCKI))
      • 14:45
        Null String Theory 45m
        Speaker: Prof. Mohammad M. Sheikh-Jabbari (Institute for Research in Fundamental Sciences)
      • 15:30
        Break 30m
      • 16:00
        Love is in the air [online] 45m
        Speaker: Prof. Sumanta Chakraborty (Indian Association for the Cultivation of Science)
      • 16:45
        Prospects of Experimental Gravity with Black Hole Imaging 45m
        Speaker: Prof. Prashant Kocherlakota (Chennai Mathematical Institute)
    • 17:30 → 18:00
      Ceremony: Closing Ceremony
    • 18:00 → 20:00
      Dinner 2h
  • Tuesday, 10 November
    • 08:00 → 12:00
      Departure
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