引力波天文课题组 GW Astronomy Group

Black hole ringdown modes are fundamental properties of the black hole spacetime. They are deeply connected to physics laws such as the No-hair theorem, Weak Cosmic Censorship and can be used to test the Area Law (2nd law of Black Hole Thermodynamics). There are many ongoing efforts regarding the excitation and characterization of black hole ringdown modes, the nonlinear regime, the spectral instability, as well as their detection in recent LVK events.

Recent Works:

• Nonlinear Ringdown at the Black Hole Horizon
• Emergent Turbulence in Nonlinear Gravity
• Quadratic Mode Couplings in Rotating Black Holes and Their Detectability
• Excitation of Quadratic Quasinormal Modes for Kerr Black Holes

Einstein’s theory of relativity is a nonlinear theory that includes many interesting phenomena, some of them are relevant for astrophysical sources. Recently we have been interested in studying the motion of an extreme mass-ratio inspiral (EMRI, a supermassive black hole + a stellar-mass companion) and its astrophysical implications (such as the environmental effects). Such system can be used to precisely measure the black hole spacetime, search for potential ultralight particles and probe its astrophysical environments.

Recent Works:

• Tidal Resonance: Tidal Resonance in Extreme Mass-Ratio Inspirals
• Wet EMRI:
  • Formation rate of extreme mass ratio inspirals in active galactic nuclei
  • Science Opportunities of Wet Extreme Mass-ratio Inspirals
• EMRI Formation Channels and Population Distributions: Probing Formation Channels of Extreme Mass-Ratio Inspirals

Binary neutron star systems may exhibit interesting matter effects. The gravitational wave measurement together with electromagnetic observation can be used to infer the structure of star, the equation of state and probe nuclear physics in the high density (and/or high temperature) regime.

Recent Works:

• Fast Radio Bursts: Repeating fast radio bursts from neutron star binaries: Multiband and multimessenger opportunities
• Neutron Star deformationProbing Crust Meltdown in Inspiraling Binary Neutron Stars
• Neutron Star relativistic resonance: Relativistic Excitation of Compact Stars

Ultralight fields or axion-like particles may accumulate around black holes via superradiance. We explore how these fields affect binary dynamics and use GW waveforms to search for physics beyond the Standard Model.

Recent Works:

• First Constraints on Nuclear Coupling of Axionlike Particles from the Binary Neutron Star Gravitational Wave Event GW170817
• Dynamic signatures of black hole binaries with superradiant clouds
• Dynamical Instability of Self-Gravitating Membranes
• Extreme Mass-ratio Inspiral within an Ultralight Scalar Cloud Scalar Radiation

We propose a type of third-generation ground-based gravitational wave detector that has superior sensitivity at kilo hertz frequency band. There detectors can accurately measure the gravitational waves from the post-merger stage of binary neutron star mergers.

Recent Works:

• Gravitational-Wave Detector for Postmerger Neutron Stars: Beyond the Quantum Loss Limit of the Fabry-Perot-Michelson Interferometer
• Exploring the sensitivity of gravitational wave detectors to neutron star physics
• Towards the design of gravitational-wave detectors for probing neutron-star physics

• Fundamental Quantum Limits for Detecting Ultrahigh Frequency Gravitational Waves

The traditional event search and parameter estimation assumes stationary, Gaussian noise which may become problematic as the signal SNR (signal-to-noise-ratio) increases. Some of the processes may not have precise waveform, such as the post-merger emission of binary neutron stars and supernovae explosion. We shall need more innovative methods to deal with these data analysis problems.

Recent Works:

• Using machine learning to parametrize postmerger signals from binary neutron stars
• GW231123: A Case for Binary Microlensing in a Strong Lensing Field