Gravitational Wave Astronomy Research Group

Introduction

The Gravitational Wave Astronomy Research Group was just established in 2024 and currently has one faculty member and one student.

We are members of the Space-borne Gravitational Wave Detector LISA Consortium and the Ground-based Gravitational Wave Detector LIGO Scientific Collaboration.

The main research direction of the research group is gravitational wave detection and various mechanisms of generating gravitational waves. PhD and postdoc candidates are welcome to apply for our open positions.

Our Work

Professor Yang Huan's work can be found at:

https://ui.adsabs.harvard.edu/public-libraries/ZZiMtNEwRKuc4iBT4itlfQ

（P.S. Prof. Yang Huan's LIGO Collaboration papers are not included in this list.）

https://scholar.google.com/citations?hl=en&user=gTIVasAAAAAJ

Research

• Black hole perturbation and ringdown study

  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 LIGO-Virgo events.

  Recent highlights:

  https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.231401

  https://arxiv.org/abs/2401.15516

  
• Strong-field dynamics

  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 highlights:

  We have discovered a new phenomenon called the “tidal resonance”, read https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.101103to find out more.

  We have shown that accretion disks will accelerate EMRI formation, so that space borne gravitational wave detectors may see many “Wet EMRIs”, which are ideal multi-messenger sources：https://journals.aps.org/prd/abstract/10.1103/PhysRevD.103.103018

  
• Compact stars and multi-messenger astronomy

  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.

  Our recent works regarding matter effects of binary neutron stars include:

  Some of the neutron star binaries may contain Fast Radio Burst (FRB) emitters in the inspiral stage, as they can be assembled directly at small separations. Read :https://journals.aps.org/prd/abstract/10.1103/PhysRevD.108.063014to learn about the signatures of FRB emissions in a binary system.

  We have shown that crusts of neutron stars may deform, yield and dissipates kinetic mode energy during the inspiraling stage of a binary neutron star system. The crust may heart up and melt down, giving rise unique signatures in the gravitational waveform:https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.201102

  
• Searching for fundamental fields and tests of General Relativity

  Light scalar/vector fields or Axion-like particles (which may also be Dark Matter candidates) may accumulate around black holes through the black hole superradiance effect. They may also be generated through coupling with the Standard Model sector. Their presence may affect the motion of compact binaries with various mass ratios, leaving an imprint on the gravitational waveform.

  Recent highlights:

  Using binary neutron stars to search for beyond-standard-model particles:https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.161101

  Understanding the dynamic signatures of binary systems with Axion clouds: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.101.043020

  
• Gravitational wave detector

  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.

  Read these articles to see the evolution of design studies and science cases:

  https://journals.aps.org/prx/abstract/10.1103/PhysRevX.13.021019

  https://journals.aps.org/prd/abstract/10.1103/PhysRevD.99.102004

  https://journals.aps.org/prd/abstract/10.1103/PhysRevD.98.044044

  
• Gravitational Wave data analysis

  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.

  Research highlights:

  We have used an AI architect called conditional variational autoencoder to build flexible and robust waveforms for post-merger waveforms of hypermassive neutron stars. Read more:https://journals.aps.org/prd/abstract/10.1103/PhysRevD.105.124021

  

Member

Professor Huan Yang

Professor Huan Yang obtained the Bachelor degree from Caltech in 2007 and PhD from Caltech in 2013. He was a postdoc fellow in Perimeter Institute from 2013-2016 and Princeton University in 2017. Since 2017 he joined the faculty in Perimeter Institute and Guelph University. Starting in April 2024 he joined the Department of Astronomy in Tsinghua University as a tenured associate Professor. His main research area is gravitational wave astronomy and strong-gravity astrophysics.

Houyi Sun

Sun Houyi graduated from Huazhong University of Science and Technology with a bachelor's degree and will be pursuing a doctoral degree at Tsinghua University in September 2024.