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Enrico Barausse24/08/2026, 09:00
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Richard Brito (CENTRA, Instituto Superior Técnico, Lisbon)24/08/2026, 09:30
Future space-based gravitational-wave observatories will open a unique avenue to study the environments surrounding black holes, in particular through the detection of extreme mass-ratio inspirals. In this seminar I will discuss the dynamics and gravitational-wave signatures of extreme mass-ratio inspirals evolving in scalar cloud environments — bosonic condensates that can grow around...
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Giovanni Maria Tomaselli24/08/2026, 10:30
Ultralight bosons can be produced by rotating black holes through superradiance, forming so-called "gravitational atoms". When these are part of a binary system, they give rise to a rich phenomenology. In this talk, I focus on two distinct scenarios. First, for an inspiralling compact binary, I show that the combination of infinitely many resonances and the "ionization jumps" creates a smooth...
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Andrea Maselli (Gran Sasso Science Institute)24/08/2026, 11:00
Asymmetric binaries, such as extreme- and intermediate-mass-ratio inspirals, are prime targets of future gravitational-wave detectors and offer a unique opportunity to probe the astrophysical environments in which such binaries evolve, as well as to test possible deviations from general relativity. To date, these two classes of effects — beyond-vacuum environmental physics and beyond-GR...
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Wenbiao Han (SHAO)24/08/2026, 14:00
Near-extremal Kerr black holes support zero-damped modes (ZDMs), whose small time-domain damping rates make them long-lived probes of the near-horizon region. We show that bound extreme-mass-ratio inspirals (EMRIs) can resonantly drive this response in vacuum general relativity.
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Using frequency-domain Teukolsky amplitudes for eccentric-inclined Kerr geodesics, we identify a source-supported... -
Zhiren Wang (Perimeter Institute & University of Waterloo)24/08/2026, 14:00
Scalar ultralight boson clouds around rotating black holes can generate long-lived, non-axisymmetric gravitational perturbations capable of exciting coherent dynamical responses in nearby accretion flows. Focusing on black hole X-ray binaries, we investigate whether this forcing can excite global oscillations of a thin accretion disk and produce observable quasi-periodic variability. Using a...
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Zhen Zhong24/08/2026, 14:15
Ultralight bosonic fields are compelling dark matter candidates. In particular, massive spin-2 fields can not only extract energy from rotating black holes via superradiant instabilities but also trigger a unique monopolar instability—specifically, the axisymmetric (azimuthal number m = 0) instability—which can even affect non-rotating black holes. This instability dominates in most of the...
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Yu-Ming Yang (IHEP)24/08/2026, 14:15
As an alternative theory to cold dark matter (CDM), fuzzy dark matter (FDM) has recently attracted widespread attention. FDM consists of ultra-light bosons with masses around 10^{-22} eV. At typical galactic velocities, their de Broglie wavelength can reach kiloparsec (kpc) scales, thereby exhibiting unique wave-like behavior on galactic scales. This leads to complex evolutionary dynamics and...
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Guangzhou Guo (Tsung-Dao Lee Institute)24/08/2026, 14:30
Tidal interactions in compact binaries excite neutron-star oscillations and reshape the late inspiral. Semi-analytic studies predict that, as merger approaches, the growing tidal deformation couples stellar modes and shifts their frequencies. We compare nonlinear hydrodynamic evolutions with a coupled-mode treatment of the quadrupolar f-mode. For moderate tides, the measured shift follows the...
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Chen Sun (HIAS-UCAS)24/08/2026, 14:30
Many well-motivated UV theories contain bonsonic light degrees of freedom, which can exhibit various wave-like behaviors at low energy. This leads to many new ideas and novel observables in recent years to probe new physics in astrophysical and laboratory setups alike. In this talk, I will briefly review a few examples in leveraging the wave-like features to test axions and ultralight dark...
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Han-Wen Hu (ITP-CAS)24/08/2026, 14:45
Conformally related black hole metrics have been reported to exhibit both conformal factor dependent and independent quasinormal mode (QNM) spectra. We show that these two outcomes correspond to different boundary value problems and resolve the apparent discrepancy in four dimensions. We reduce the Bach perturbation equations to two coupled radial equations of second order. For the...
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Fengwei Yang (University of Notre Dame)24/08/2026, 14:45
The existence of a superradiant axion cloud around a black hole X-ray binary can heat its accretion disk and be detected in a thermal X-ray spectrum. We consider a derivative coupling between axions and fermions and calculate the emissivity of the inverse bremsstrahlung process, which results in a temperature fluctuation of the disk. The energy injection rate per baryon by axion heating is...
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Chen Yuan (Shanghai University)24/08/2026, 15:00
Gravitational waves open a new window onto black holes and their surrounding environments. Realistic environments such as ultralight bosonic fields and accretion environments can leave observable signatures in gravitational wave signals. This talk explores how such environmental effects can be used to probe fundamental physics and astrophysics. Topics include gravitational waves from...
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jianing Chen (HIAS, UCAS.)24/08/2026, 15:00
Environmental effects can modify quasinormal-mode spectra and affect their physical interpretation. We model such effects by adding a localized Gaussian random perturbation to the analytically solvable Pöschl–Teller potential. Using logarithmic perturbation theory and the generalized QNM norm, we derive the first- and second-order frequency corrections to the fundamental mode while treating...
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Zhi-Qing Zhu (ICTP-AP)24/08/2026, 15:15
We investigate black hole superradiance evolution of the interacting multiple fields. We consider a model of two scalar fields interacting with a cubic coupling, and study the superradiant evolution of the cloud. We demonstrate that superradiance is typically suppressed when the superradiant field couples to another field, even with a very weak coupling strength. This implies that the...
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Liang-Bi Wu (HIAS UCAS)24/08/2026, 15:15
We present a study of virtual absorption modes (VAMs) in Schwarzschild-de Sitter (SdS) spacetime under semi-open boundary conditions, where the VAMs correspond to total transmission modes (TTMs) with the reflection amplitude being vanishing. Our numerical analysis reveals that as the reflectivity $|\mathcal{K}|$ decreases, the VAM spectra migrate systematically toward regions of less negative...
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Ximeng Li (TDLI)24/08/2026, 16:00
Axion fields can form exponentially growing gravitational clouds around compact objects through self-interaction–driven relaxation of ambient axion waves. As the field amplitude approaches the axion decay constant, nonlinear effects become important. We identify two distinct regimes of late-time evolution, determined by the gravitational fine-structure constant and the cloud growth rate: a...
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Qi Su (Beijing University of Technology)24/08/2026, 16:00
Layering is an ubiquitous feature of astrophysical objects. Motivated by the fact that physical black holes retain such structures in the time definition all outside probes are selected and monitored, we investigate linear perturbations and gravitational-wave echoes of a compact object composed of two concentric thin shells. Compared with the single-shell configuration, the double shell...
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Dr Hailin Xu (Tsung-Dao Lee Institute)24/08/2026, 16:15
Quadratically coupled ultralight scalar dark matter behaves as a coherent classical field whose interactions with matter can induce a composition-dependent force through the dark matter background. We present a complete calculation of this background-induced force beyond the spherically symmetric approximation. Using a partial-wave treatment of dark-matter scattering, we determine its angular...
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Jerome Mecca ((1) University of Northern Philippines, (2) National Institute of Physics, University of the Philippines Diliman)24/08/2026, 16:15
The self-force acting on a charged particle is sensitive to the global structure of curved spacetime and can serve as a probe of geometry beyond local curvature. We compute the static scalar self-force on a point charge in the two-parameter family of spherically symmetric wormholes introduced by Konoplya and Zhidenko, members of the broader Morris–Thorne class of traversable wormholes. Using...
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Ziwen Yin (Tsung-Dao Lee Institute & SJTU)24/08/2026, 16:30
The orbital evolution of the Hulse-Taylor binary neutron star system is described with high precision by General Relativity, in which gravity is the only long-range force and gravitational waves provide the dominant energy-loss channel. We use this precision test of relativistic binary dynamics to derive new constraints on axion couplings to stable neutron-star constituents: neutrons,...
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Shaoqi Hou24/08/2026, 16:30
Soft hairs of black holes are the Noether charges associated with the generalized Bondi-Metzner-Sachs symmetries. In this work, the images of soft-haired Kerr black holes are studied. For an eternal black hole, the image is rotated, dilated, and drifting compared to that of the bald counterpart in the celestial plane. The rotation and the dilation are independent of time, while the drifting...
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Zhen-Hong Lyu (Institute of Theoretical Physics, Chinese Academy of Sciences)24/08/2026, 16:45
Ultralight bosons around spinning black holes can form macroscopic gravitational atoms through superradiance. We show that attractive self-interactions can turn such systems into periodically varying lenses for gravitational waves. During the long-lived 211–322 quasi-equilibrium, coherent interference between the dominant 211 cloud and the self-interaction-populated 322 level produces an...
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Yu-Sen Zhou (University of Science and Technology of China)24/08/2026, 16:45
The surface $r=\infty$ in the Kerr--Bertotti--Robinson (KBR) spacetime is known not to be a physical boundary. We explicitly construct a natural extension across it, obtaining a wormhole that connects the exterior of one KBR black hole to the interior of a neighboring one. Depending on the parameters, the extended spacetime exhibits several distinct global causal structures and can contain a...
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Yanjie Zeng (Peking University)24/08/2026, 17:00
The Event Horizon Telescope (EHT) has significantly advanced our ability to study black holes, achieving unprecedented spatial resolution and revealing horizon-scale structures. Notably, these observations feature a distinctive dark shadow—primarily arising from faint jet emissions—surrounded by a bright photon ring. Anticipated upgrades of the EHT promise substantial improvements in dynamic...
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Dingfang Zeng (Beijing University of Technology)24/08/2026, 17:00
XOB provides an eXact One-Body approach to the conservative part of binary dynamics in General Relativity. We will report that dynamics of this approach under the weak-field-low-speed expansion is equivalent to the post-newtonian approximation at all orders, thus making it a truly GR-version one-body formulation of two-body problems. Using this approach and a banana-shape-deformation modulated...
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Xi-Li Zhang (IHEP,CAS)24/08/2026, 17:15
The growing sensitivity of gravitational-wave detectors enables increasingly precise tests of black hole (BH) ringdown spectroscopy. Yet BH quasinormal modes (QNMs) are spectrally unstable: small near horizon modifications can produce a drastically different QNM spectrum, while causality requires the prompt ringdown to remain BH-like until the reflected signal returns. Quantum BHs with...
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Yuxin Liu24/08/2026, 17:15
Neutron stars are known to constrain asymmetric dark matter because accumulated particles can trigger collapse. I will show that these constraints extend much further: even when dark matter is produced with equal particle and antiparticle abundances, the capture process inside a neutron star can become intrinsically asymmetric if the two species scatter off nucleons with slightly different...
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Gilad Perez25/08/2026, 09:00
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Diego Blas (ICREA/IFAE)25/08/2026, 09:30
I will present GUEST, a current proposal showing how satellite laser ranging of two tests masses in properly chosen orbits may be sensitive to GWs backgrounds/events in the microHz band at levels where one expect signals from different phenomena.
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Xiaojun Bi (Institute of High Energy Physics, Chinese Academy of Sciences)25/08/2026, 11:00
Ultralight dark matter (ULDM) has attracted significant attention as a compelling alternative to cold dark matter, yet it faces increasingly stringent constraints from observations of compact stellar systems and satellite galaxies. In this talk, I present a series of numerical simulation studies from our group that systematically reexamine these constraints. We first show how the almost-dark...
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Bo-Xuan Ge25/08/2026, 14:00
Numerical-relativity data are not generic arrays to be enhanced, but
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discretized geometric fields constrained by the Einstein equations. We
introduce AI(\times)NR-Pathfinder, a constraint-aware learning framework
that applies small, stencil-consistent correction operators to
(3+1) numerical-relativity slices while preserving the algebraic
structure of the conformal variables. The... -
Sk Jeesun25/08/2026, 14:00
Current multi-tonne-scale dark matter (DM) detectors are largely incapable of detecting light dark matter from the Galactic halo due to the energy threshold limitations of their recoil measurements. However, primordial black holes (PBHs) can evaporate via Hawking radiation to particles whose energies are set by the black hole temperature. Consequently, weakly interacting light dark matter (or...
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Alejandra Gonzalez (University of the Balearic Islands)25/08/2026, 14:15
We present 52 new numerical-relativity (NR) simulations of black-hole-neutron-star merger (BHNS) mergers and employ the data to inform a multipolar effective-one-body model for complete waveforms from arbitrary mergers. Our simulations target quasicircular mergers and the parameter space region characterized by significant tidal disruption of the star. Convergent gravitational waveforms are...
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Qiyuan Gao (ICTP-AP & University of Chinese Academy of Sciences)25/08/2026, 14:15
We identify the Standard Model–charged portal multiplets that can connect the visible sector to a massive dark photon while preserving an exact dark charge conjugation that protects it from decay. Requiring the Standard Model gauge fields to remain invariant under this symmetry forces the portal to carry zero hypercharge and to transform in self-conjugate representations of (SU(3)_c\times...
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Kunyang Li (Center for Computational Astrophysics, Flatiron Institute)25/08/2026, 14:30
Low-frequency gravitational-wave surveys need not just how often massive black holes (MBHs) merge, but the parameters carried to coalescence: masses, mass ratio, spins, eccentricity, and the delay since galaxy assembly. These depend on dynamical regimes that cosmological galaxy simulations cannot resolve. We extend RAMCOAL, a subgrid model in the RAMSES hydrodynamical code, to follow MBH...
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Hongyi Jiang (Tsinghua University)25/08/2026, 14:30
In this talk, we studied heavy particle production from bubble collisions, and we show that by analyzing the trapping equation, the efficiency factor in the high-frequency regime behaves as $f(\chi) \sim \chi^{-4}$, a result we then generalize to $3+1$ dimensions while confirming the same power-law suppression.
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专 宁25/08/2026, 14:45
We present a numerical-relativity study of comparable-mass boson star-black hole (BS-BH) head-on collisions, focusing on both initial-data construction and gravitational-wave (GW) phenomenology. We show that plain superposition can strongly perturb the BS core, leading to large constraint violations and unphysical radial oscillations. To remedy this problem, we introduce a one-body...
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Ajay Kaladharan (ICTP-AP)25/08/2026, 14:45
Strongly Interacting Massive Particles (SIMPs) provide an intriguing alternative to conventional collisionless dark matter (CDM) scenarios, particularly in light of tensions between CDM predictions and observations on small astrophysical scales. In SIMP models, the observed dark matter relic abundance is generated through self-annihilation processes such as $3 \to 2$ or $4 \to 2$, involving...
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Jian-dong Zhang (Sun Yat-sen Univeristy)25/08/2026, 15:00
The major challenge for the fast generation of such waveforms is the generation of the Teukolsky amplitudes for generic (eccentric and inclined) Kerr orbits. The requirement forthe modeling of ∼ 10^5 harmonic modes across a four-dimensional parameter space makes traditional approaches, including direct computation or dense interpolation, computationally prohibitive. To overcome this issue, we...
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Ayush Hazarika (International Center for Theoretical Physics Asia-Pacific (ICTP-AP), University of Chinese Academy of Sciences)25/08/2026, 15:00
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...
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Filip Pozar (Rudjer Boskovic Institute)25/08/2026, 15:15
Noncommutative/quantum geometry is the program of studying geometry on noncommutative algebras (modeling quantum coordinates and spacetime functions) endowed with some extra structure (Dirac operator and Hilbert space) giving rise to a spectral triple. It is well known that a special noncommutative geometry, via the spectral action principle, uniquely leads to the classical Standard Model...
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Yuhe Zeng (Tsung-Dao Lee Institute, Shanghai Jiao Tong University)25/08/2026, 15:15
A small body orbiting around an accreting massive object and periodically crossing its accretion disk is a
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common configuration in astrophysics. In this work, we study the secular evolution of extreme mass-ratio
inspirals (EMRIs), where a stellar-mass object (SMO)—such as a star or a stellar-mass black hole (sBH)—
collides with the accretion disk surrounding a central supermassive black... -
Haitian Wang (Dalian University of Technology)25/08/2026, 16:00
Gravitational-wave observations offer a powerful way to probe compact binary coalescences and test strong-field gravity. In this talk, I will present a preliminary study on gravitational-wave data analysis using the F-statistic, focusing on its applications to black-hole ringdown and full inspiral–merger–ringdown analyses. By analytically maximizing over amplitude-related parameters, the...
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Alejandro Torres-Orjuela (Beijing Institute of Mathematical Sciences and Applications (BIMSA))25/08/2026, 16:00
Standard sirens - gravitational wave (GW) sources with an electromagnetic (EM) counterpart - can be used to measure the Hubble constant directly and thus will help to ease the Hubble tension. However, systems that emit detectable GWs and EM radiation at the same time are rare. Therefore, binary black hole (BBH) mergers inside active galactic nuclei (AGNs) are gaining more and more attention as...
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Uddeepta Deka (Shanghai Astronomical Observatory - Chinese Academy of Sciences)25/08/2026, 16:15
Gravitational-wave (GW) microlensing occurs when an intervening compact object diffracts the GW in the wave-optics regime, imprinting characteristic frequency-dependent modulations on the observed signal. Current searches for microlensing signatures in the detected GW events assume an isolated point mass lens (PML) model. However, this assumption is overly simplistic. Astrophysical microlenses...
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Hanlin Song (Institute of Mechanics, Chinese Academy of Sciences)25/08/2026, 16:15
Multimessenger gravitational-wave observations provide a powerful probe of fundamental gravity in the strong-field and dynamical regime. In this work, we test possible deviations from general relativity from two complementary perspectives: a temporal variation of the gravitational constant, which is closely related to the strong equivalence principle, and the existence of hidden compact extra...
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Anson Chen (International Centre for Theoretical Physics - Asia Pacific)25/08/2026, 16:30
Cosmic acceleration may arise from modifications to gravity that become significant on large scales. In many scalar–tensor and effective-field-theory models, an evolving gravitational coupling changes the friction experienced by gravitational waves (GWs), causing their luminosity distance to differ from the electromagnetic prediction. In this talk, I will present constraints on...
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Hanyu Cheng25/08/2026, 16:30
Pulsar timing arrays are becoming sensitive to individual supermassive black hole binaries above the nanohertz gravitational-wave background. I will present a harmonic-space framework that consistently incorporates irregular pulsar sampling, non-uniform noise, source confusion, and pulsar terms. By marginalizing over unknown pulsar phases, we obtain a parameter-dependent covariance and derive...
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Qimin Song (International Centre for Theoretical Physics-Asia Pacific (ICTP-AP))25/08/2026, 16:45
Subsolar-mass exotic compact objects (ECOs) are a possible clue to new physics beyond conventional astrophysics. When such an object orbits a stellar-mass black hole or neutron star, the resulting binary is a mini extreme mass-ratio inspiral (mini-EMRI) system. Gravitational waves emitted by mini-EMRI systems can last from hours to years in LIGO's frequency band, with characteristics closely...
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迈 乔 (International Centre for Theoretical Physics Asia-Pacific, University of Chinese Academy of Sciences)25/08/2026, 16:45
The stochastic gravitational-wave backgrounds are expected to arise from the superposition of many individually unresolved sources throughout cosmic history, carrying information about compact-binary populations, gravity beyond general relativity, and possible processes in the early Universe. In this talk, I will present recent progress in the LIGO-Virgo-KAGRA search for an isotropic...
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Mr Shitong Guo (Nankai University)25/08/2026, 17:00
Gravitational-wave ringdowns encode the characteristic oscillation spectrum of the compact remnant and provide a direct probe of strong-field gravity. Yet conventional analyses usually infer remnant properties with theory-specific waveform templates, entangling the information extracted from the data with the assumed model. Ringdown inference is also often treated in isolation, leaving aside...
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Mr zheng WU (L2IT)25/08/2026, 17:00
We investigate the detectability of line-of-sight acceleration (LOSA) in gravitational-wave signals from massive binary black holes (MBHBs) observable by LISA. A constant LOSA introduces a $-4$PN correction to the inspiral phase, which we derive and implement in the \texttt{LISAbeta} analysis pipeline.
Our Bayesian analysis reveals that LOSA measurement precision depends strongly on total...
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Charchit Kumar Sethi (International Center for Theoretical Physics, Asia Pacific (ICTP-AP)/ University Chinese Academy of Sciences (UCAS,中国科学院大学))25/08/2026, 17:15
Primordial black holes (PBHs) are compelling dark matter (DM) candidates; however, current observational constraints indicate that they can not account for the entirety of the DM abundance. This motivates scenarios in which additional DM components coexist with PBHs and form dense structures, often referred to as ``dark dresses,'' around them. Such environments induce dynamical friction,...
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Muchun Chen (TDLI)25/08/2026, 17:15
The final-parsec problem has long posed a central challenge in understanding the merger of supermassive black hole binaries. In this paper, we investigate a scenario in which a dark scalar or vector field is sourced by eccentric binaries, leading to accelerated mergers through additional dipole radiation and thereby extending the range of masses for which the binary can merge within a Hubble...
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Avi Vajpeyi (University of Auckland)25/08/2026, 17:30
Accurate and scalable noise modelling will be essential for extracting weak gravitational-wave signals and signatures of new physics from LISA data. Realistic time-delay interferometry channels may contain frequency-dependent correlations, while the detector noise may also evolve over the mission.
I will present a Bayesian framework for estimating the full spectral density matrix of...
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Han Wang (Peking University)25/08/2026, 17:30
Additional fundamental fields can modify compact-binary radiation, with dipole-radiation effects entering most strongly during the early inspiral. Although binary black holes do not emit leading-order dipole radiation in many commonly studied theories, more general scenarios can endow them with effective charges or additional radiation channels. Space-ground multiband observations therefore...
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Eugene Lim26/08/2026, 09:00
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Haipeng An (Tsinghua University)26/08/2026, 09:30
I will discuss the vacuum decay processses that may happen in the early universe and the properties of the corresponding gravitational wave signals.
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Shao-Jiang Wang (Institute of Theoretical Physics, Chinese Academy of Sciences)26/08/2026, 10:30
In this talk, I will introduce our recent progress on cosmological first-order phase transitions, primordial black holes, scalar-induced gravitational waves, and sound waves from gravitational instability.
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Hyungjin Kim27/08/2026, 09:00
In this talk, I will discuss stochastic fluctuations of wave dark matter. I will discuss what it means and how we can utilize such stochastic density fluctuations of wave dark matter to probe its existence only via gravitational interaction. I will discuss a few specific observational and experimental setup, including inteferometry, pulsar timing, astrometry, and interplanetary range measurements.
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Arianna Foschi27/08/2026, 09:30
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Rodrigo Luís Lourenço Vicente27/08/2026, 10:30
Gravitational-wave (GW) observations allow us to reconstruct the orbital dynamics of compact binaries with remarkable precision. When these systems evolve in dense environments—such as active galactic nucleus discs, nuclear star clusters, or dark matter structures—their surroundings can leave characteristic imprints on the GW phase evolution. These imprints open a new avenue for probing not...
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Hai-Bo Yu27/08/2026, 11:00
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Takuya Takahashi (The University of Tokyo)27/08/2026, 14:00
Extreme mass ratio inspirals (EMRIs) are among the key targets for future gravitational wave observations. While the study of EMRIs in vacuum has been extensively developed over the past decades, environmental effects arising from matter surrounding black holes have also attracted significant attention in recent years. A proper understanding of such effects may open up the possibility of...
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Zhiren Wang (Perimeter Institute & University of Waterloo)27/08/2026, 14:00
Scalar ultralight boson clouds around rotating black holes can generate long-lived, non-axisymmetric gravitational perturbations capable of exciting coherent dynamical responses in nearby accretion flows. Focusing on black hole X-ray binaries, we investigate whether this forcing can excite global oscillations of a thin accretion disk and produce observable quasi-periodic variability. Using a...
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Himanshi Gulia (Netaji Subhas University of Technology)27/08/2026, 14:15
The Event Horizon Telescope images of M87 and Sgr A give us a unique chance to test gravity in the strong field regime and assess deviations from the Kerr solution. We study the shadows of rotating nonsingular black holes—namely, generalized Ghosh black holes (GGBHs), given by the mass function $m(r) = M e^{-(k/r)^n}$, which reduces to the Kerr black hole ($k \to 0$) and to the original...
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Qi-Xuan Xu (Instituto Superior Técnico)27/08/2026, 14:15
Through black hole superradiance, ultralight bosonic fields may form macroscopic clouds around rotating black holes. Extreme-mass-ratio inspirals (EMRIs), among the primary targets of future space-based gravitational-wave detectors, provide a unique opportunity to probe such environments. We extend the relativistic perturbative framework for EMRIs within scalar clouds from circular, equatorial...
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江川 于 (北京大学)27/08/2026, 14:30
The dense environment of our Galactic Center (GC) offers a unique laboratory for probing ultralight dark matter (ULDM). We explore the prospect of detecting a scalar ULDM field through its effects on the orbital dynamics of S-stars around the supermassive black hole in the GC, Sgr A$^*$. We consider both linear and quadratic couplings between the real scalar field $\phi$ and Standard Model...
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Ariadna Uxue Palomino Ylla (Nagoya University)27/08/2026, 14:30
Black-hole ringdown provides a promising way to test deviations from the Kerr geometry, especially when compact objects are surrounded by matter fields or effective hair. In this work, we study how small deviations from Schwarzschild and Kerr spacetimes modify the eikonal quasinormal-mode spectrum through the properties of unstable circular null geodesics. We derive first-order shifts in the...
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Shalabh Gautam (Beijing Institute of Mathematical Sciences and Applications (BIMSA))27/08/2026, 14:45
This talk summarises our recent work on a fully 3D Summation-by-Parts scheme for a class of linear wave equations on hyperboloidal slices. The scheme is derived in spherical polar coordinates on a Minkowski background, and allows having grid points at the origin and on the z-axis, despite coordinate singularities, and at infinity, by introducing compactification followed by rescaling, and is...
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Ao Guo (International Centre for Theoretical Physics Asia-Pacific, University of Chinese Academy of Sciences, 100190 Beijing, China)27/08/2026, 14:45
Ultralight bosons, such as axion-like particles, are promising candidates for physics beyond the Standard Model. Rotating black holes can amplify these fields through superradiance, forming macroscopic bosonic clouds known as gravitational atoms. In this work, we investigate the evolution of ultralight boson clouds in binary black hole systems, considering their full evolutionary history from...
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Masaki Kitagawa (Department of Physics, Faculty of Science, Tokyo University of Science)27/08/2026, 15:00
We construct and classify asymptotically flat, static, and spherically symmetric hairy black hole solutions in $U(1)$ gauge-invariant scalar-vector-tensor (SVT) theories [1] carrying both electric and magnetic charges. Extending previous analyses beyond the second-order SVT interaction [2], we include the third- and fourth-order SVT interactions in dyonic backgrounds [3]. We show that the...
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Yuhao Guo27/08/2026, 15:00
Detection of gravitational waves enables probes of environmental effects around compact binaries. Ultralight bosons, well motivated in particle physics and capable of forming core-like dark matter structures, induce environmental dynamics that differ qualitatively from
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those produced by stars or particle dark matter. For comparable-mass binaries, such bosons can form gravitationally bound... -
Mr Shunta Nishimura (Department of Physics, Faculty of Science Tokyo University of Science, Japan)27/08/2026, 15:15
We investigate the linear stability of static, spherically symmetric dyonic black hole solutions carrying both electric and magnetic charges in the U(1) gauge-invariant scalar-vector-tensor theory [1]. In the limit of vanishing magnetic charge, our framework reproduces the results of previous studies [2,3]. With appropriate choices of the interaction functions, it also encompasses the...
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Jing Ren28/08/2026, 09:00
Ultralight axion‑like dark matter (ALDM) is a well‑motivated candidate whose wave‑like nature is manifest on astronomical scales. Pulsar timing arrays (PTAs) and pulsar polarization arrays (PPAs) offer complementary probes: PTAs search for ALDM imprints on pulse arrival times, while PPAs target linear polarization angle rotations induced by the axion–photon Chern–Simons coupling. In this talk,...
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Hidetoshi Omiya28/08/2026, 09:30
In recent years, black hole superradiance, extraction of energy and angular momentum from a rotating black hole, has attracted considerable attention as a probe of light bosonic particles.
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For a massive bosonic field, superradiance can lead to an instability and the growth of a macroscopic boson cloud, which may subsequently emit gravitational waves.
The cloud is often said to be seeded by... -
Nils Siemonsen28/08/2026, 10:30
Gravitational and electromagnetic signatures of black hole
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superradiance are a unique probe of ultralight particles that
are weakly-coupled to ordinary matter. I will highlight the importance
of such non-minimal couplings as well as self-interactions
on observational signatures and present recent constraints on these
particles obtained from gravitational wave data. -
宏 Hong 张 Zhang (山东大学 Shandong University)28/08/2026, 11:00
An ultralight real scalar field could form a localized condensate under gravity, either with an external gravitational field such as the boson cloud around a black hole, or with self-gravity such as a boson star. Different from the complex scalar field, the real scalar cannot form vortices. Then how does the localized condensate take angular momentum? In this talk, I will explain the...
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Kfir Blum
Decades of direct and indirect detection attempts via hypothesized non-gravitational interactions of dark matter yielded, so far, only null results.
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Existing positive evidence is overwhelming, but purely gravitational. This motivates a program for widening and deepening the scope of gravitational probes: highlighting observational data and attempting to detect, understand, and solve — from...
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