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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... -
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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