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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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,...
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...
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。
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...
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...
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...
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...
During last decade and a half many results are obtained that show when (i) particle collisions in a strong gravitational field lead to an unbounded energy in the center of mass E_{c.m.} of two colliding particles, (ii) when the process leads also to significant energy extraction measured at infinity. The set of possible scenarios can be divided to three main cases: (i) collisions near black...
Possible existence of antimatter at astrophysical and cosmological scales is considered. It is shown that the model of primordial black hole of 1993 may lead to a noticeable populations of our Galaxy with diferent forms of
antimatter and observational manifestations of the latter are presented.
