Dongjun Li
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Research Interests
Dongjun Li has a total of 55 co-authors. Here are the top co-authors by number of shared publications:
Yanbei Chen
Theoretical Astrophysics California Institute of Technology 350-17 91125 Pasadena CA USA
8 shared publications- Pratik Wagle
Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
6 shared publications - Yanbei Chen
California Institute of Technology
5 shared publications - Colin Weller
California Institute of Technology
4 shared publications - Nicolás Yunes
University of Illinois Urbana-Champaign
4 shared publications - Kathryn M. Zurek
California Institute of Technology
3 shared publications
Latest Publications
- 22 October 2025
- Published by American Physical Society (APS) in Physical Review D
- Vol. 112 (8)
Extreme mass-ratio inspiral within an ultralight scalar cloud: Scalar radiation
- 22 October 2025
- Published by American Physical Society (APS) in Physical Review D
- Vol. 112 (8)
Extreme mass-ratio inspiral within an ultralight scalar cloud: Scalar radiation
- Open Access
Evolving extreme mass-ratio inspirals in a perturbed Schwarzschild spacetime
In this work, we develop the modified Teukolsky formalism that describes the GW radiation from a point mass orbiting around a perturbed Schwarzschild BH. This perturbation of the background spacetime induces a secular change in the orbital phase of the point mass. In turn, this causes a modification in the GW flux, which can be used to probe the background spacetime. We explicitly apply this formalism to a bumpy Schwarzschild spacetime as a proof of principle. The results pave the way for the description of EMRIs in generic perturbed Kerr spacetime in future developments.
Open AccessEvolving extreme mass-ratio inspirals in a perturbed Schwarzschild spacetime
In this work, we develop the modified Teukolsky formalism that describes the GW radiation from a point mass orbiting around a perturbed Schwarzschild BH. This perturbation of the background spacetime induces a secular change in the orbital phase of the point mass. In turn, this causes a modification in the GW flux, which can be used to probe the background spacetime. We explicitly apply this formalism to a bumpy Schwarzschild spacetime as a proof of principle. The results pave the way for the description of EMRIs in generic perturbed Kerr spacetime in future developments.
- 15 October 2025
- Published by American Physical Society (APS) in Physical Review D
- Vol. 112 (8)
Ringdown of a black hole surrounded by a thin shell of matter
- 15 October 2025
- Published by American Physical Society (APS) in Physical Review D
- Vol. 112 (8)
Ringdown of a black hole surrounded by a thin shell of matter
- 5 August 2025
- Published by American Physical Society (APS) in Physical Review D
- Vol. 112 (4)
Perturbations of spinning black holes in dynamical Chern-Simons gravity: Slow rotation quasinormal modes
- 5 August 2025
- Published by American Physical Society (APS) in Physical Review D
- Vol. 112 (4)
Perturbations of spinning black holes in dynamical Chern-Simons gravity: Slow rotation quasinormal modes
- 24 January 2025
- Published by American Physical Society (APS) in Physical Review D
- Vol. 111 (2)
Spectroscopy of bumpy BHs: The nonrotating case
- 24 January 2025
- Published by American Physical Society (APS) in Physical Review D
- Vol. 111 (2)
Spectroscopy of bumpy BHs: The nonrotating case
- Open Access
- 10 May 2024
- Published by American Physical Society (APS) in Physical Review D
- Vol. 109 (10) , 104029
Perturbations of spinning black holes in dynamical Chern-Simons gravity: Slow rotation equations
The detection of gravitational waves resulting from the coalescence of binary black holes by the LIGO-Virgo-Kagra Collaboration has inaugurated a new era in gravitational physics. These gravitational waves provide a unique opportunity to test Einstein’s general relativity and its modifications in the regime of extreme gravity. A significant aspect of such tests involves the study of the ringdown phase of gravitational waves from binary black hole coalescence, which can be decomposed into a superposition of various quasinormal modes. In general relativity, the spectra of quasinormal modes depend on the mass, spin, and charge of the final black hole, but they can also be influenced by additional properties of the black hole spacetime, as well as corrections to the general theory of relativity. In this work, we focus on a specific modified theory known as dynamical Chern-Simons gravity. We employ the modified Teukolsky formalism developed in a previous study and lay down the foundations to investigate perturbations of slowly rotating black holes admitted by the theory. Specifically, we derive the master equations for the and Weyl scalar perturbations that characterize the radiative part of gravitational perturbations, as well as the master equation for the scalar field perturbations. We employ metric reconstruction techniques to obtain explicit expressions for all relevant quantities. Finally, by leveraging the properties of spin-weighted spheroidal harmonics to eliminate the angular dependence from the evolution equations, we derive two, radial, second-order, ordinary differential equations for and , respectively. These two equations are coupled to another radial, second-order, ordinary differential equation for the scalar field perturbations. This work is the first attempt to derive a master equation for black holes in dynamical Chern-Simons gravity using curvature perturbations. The master equations we obtain can then be numerically integrated to obtain the quasinormal mode spectrum of slowly rotating black holes in this theory, making progress in the study of ringdown in dynamical Chern-Simons gravity.- 10 May 2024
- Published by American Physical Society (APS) in Physical Review D
- Vol. 109 (10) , 104029
Open AccessPerturbations of spinning black holes in dynamical Chern-Simons gravity: Slow rotation equations
The detection of gravitational waves resulting from the coalescence of binary black holes by the LIGO-Virgo-Kagra Collaboration has inaugurated a new era in gravitational physics. These gravitational waves provide a unique opportunity to test Einstein’s general relativity and its modifications in the regime of extreme gravity. A significant aspect of such tests involves the study of the ringdown phase of gravitational waves from binary black hole coalescence, which can be decomposed into a superposition of various quasinormal modes. In general relativity, the spectra of quasinormal modes depend on the mass, spin, and charge of the final black hole, but they can also be influenced by additional properties of the black hole spacetime, as well as corrections to the general theory of relativity. In this work, we focus on a specific modified theory known as dynamical Chern-Simons gravity. We employ the modified Teukolsky formalism developed in a previous study and lay down the foundations to investigate perturbations of slowly rotating black holes admitted by the theory. Specifically, we derive the master equations for the and Weyl scalar perturbations that characterize the radiative part of gravitational perturbations, as well as the master equation for the scalar field perturbations. We employ metric reconstruction techniques to obtain explicit expressions for all relevant quantities. Finally, by leveraging the properties of spin-weighted spheroidal harmonics to eliminate the angular dependence from the evolution equations, we derive two, radial, second-order, ordinary differential equations for and , respectively. These two equations are coupled to another radial, second-order, ordinary differential equation for the scalar field perturbations. This work is the first attempt to derive a master equation for black holes in dynamical Chern-Simons gravity using curvature perturbations. The master equations we obtain can then be numerically integrated to obtain the quasinormal mode spectrum of slowly rotating black holes in this theory, making progress in the study of ringdown in dynamical Chern-Simons gravity. - 10 May 2024
- Published by American Physical Society (APS) in Physical Review D
- Vol. 109 (10) , 104026
Isospectrality breaking in the Teukolsky formalism
General relativity, though the most successful theory of gravity, has been continuously modified to resolve its incompatibility with quantum mechanics and explain the origin of dark energy or dark matter. One way to test these modified gravity theories is to study the gravitational waves emitted during the ringdown of binary mergers, which consist of quasinormal modes. In several modified gravity theories, the even- and odd-parity gravitational perturbations of nonrotating and slowly rotating black holes have different quasinormal mode frequencies, breaking the isospectrality of general relativity. For black holes with arbitrary spin in modified gravity, there were no avenues to compute quasinormal modes except numerical relativity, until recent extensions of the Teukolsky formalism. In this work, we describe how to use the modified Teukolsky formalism to study isospectrality breaking in modified gravity. We first introduce how definite-parity modes are defined through combinations of Weyl scalars in general relativity, and then, we extend this definition to modified gravity. We then use the eigenvalue perturbation method to show how the degeneracy in quasinormal mode frequencies of different parity is broken in modified gravity. To demonstrate our analysis, we also apply it to some specific modified gravity theories. Our work lays the foundation for studying isospectrality breaking of quasinormal modes in modified gravity for black holes with arbitrary spin.
- 10 May 2024
- Published by American Physical Society (APS) in Physical Review D
- Vol. 109 (10) , 104026
Isospectrality breaking in the Teukolsky formalism
General relativity, though the most successful theory of gravity, has been continuously modified to resolve its incompatibility with quantum mechanics and explain the origin of dark energy or dark matter. One way to test these modified gravity theories is to study the gravitational waves emitted during the ringdown of binary mergers, which consist of quasinormal modes. In several modified gravity theories, the even- and odd-parity gravitational perturbations of nonrotating and slowly rotating black holes have different quasinormal mode frequencies, breaking the isospectrality of general relativity. For black holes with arbitrary spin in modified gravity, there were no avenues to compute quasinormal modes except numerical relativity, until recent extensions of the Teukolsky formalism. In this work, we describe how to use the modified Teukolsky formalism to study isospectrality breaking in modified gravity. We first introduce how definite-parity modes are defined through combinations of Weyl scalars in general relativity, and then, we extend this definition to modified gravity. We then use the eigenvalue perturbation method to show how the degeneracy in quasinormal mode frequencies of different parity is broken in modified gravity. To demonstrate our analysis, we also apply it to some specific modified gravity theories. Our work lays the foundation for studying isospectrality breaking of quasinormal modes in modified gravity for black holes with arbitrary spin.
- Open Access
Perturbations of spinning black holes in dynamical Chern-Simons gravity I. Slow rotation equations
The detection of gravitational waves resulting by the LIGO-Virgo-Kagra collaboration has inaugurated a new era in gravitational physics, providing an opportunity to test general relativity and its modifications in the strong gravity regime. One such test involves the study of the ringdown phase of gravitational waves from binary black-hole coalescence, which can be decomposed into a superposition of quasinormal modes. In general relativity, the spectra of quasinormal modes depend on the mass, spin, and charge of the final black hole, but they can be influenced by additional properties of the black hole, as well as corrections to general relativity. In this work, we employ the modified Teukolsky formalism developed in a previous study to investigate perturbations of slowly rotating black holes in a modified theory known as dynamical Chern-Simons gravity. Specifically, we derive the master equations for the $Ψ_0$ and $Ψ_4$ Weyl scalar perturbations that characterize the radiative part of gravitational perturbations, as well as for the scalar field perturbations. We employ metric reconstruction techniques to obtain explicit expressions for all relevant quantities. Finally, by leveraging the properties of spin-weighted spheroidal harmonics to eliminate the angular dependence from the evolution equations, we derive two, radial, second-order, ordinary differential equations for $Ψ_0$ and $Ψ_4$, respectively. These equations are coupled to another radial, second-order, ordinary differential equation for the scalar field perturbations. This work is the first attempt to derive a master equation for black holes in dynamical Chern-Simons gravity using curvature perturbations. The master equations can be numerically integrated to obtain the quasinormal mode spectrum of slowly rotating black holes in this theory, making progress in the study of ringdown in dynamical Chern-Simons gravity.Open AccessPerturbations of spinning black holes in dynamical Chern-Simons gravity I. Slow rotation equations
The detection of gravitational waves resulting by the LIGO-Virgo-Kagra collaboration has inaugurated a new era in gravitational physics, providing an opportunity to test general relativity and its modifications in the strong gravity regime. One such test involves the study of the ringdown phase of gravitational waves from binary black-hole coalescence, which can be decomposed into a superposition of quasinormal modes. In general relativity, the spectra of quasinormal modes depend on the mass, spin, and charge of the final black hole, but they can be influenced by additional properties of the black hole, as well as corrections to general relativity. In this work, we employ the modified Teukolsky formalism developed in a previous study to investigate perturbations of slowly rotating black holes in a modified theory known as dynamical Chern-Simons gravity. Specifically, we derive the master equations for the $Ψ_0$ and $Ψ_4$ Weyl scalar perturbations that characterize the radiative part of gravitational perturbations, as well as for the scalar field perturbations. We employ metric reconstruction techniques to obtain explicit expressions for all relevant quantities. Finally, by leveraging the properties of spin-weighted spheroidal harmonics to eliminate the angular dependence from the evolution equations, we derive two, radial, second-order, ordinary differential equations for $Ψ_0$ and $Ψ_4$, respectively. These equations are coupled to another radial, second-order, ordinary differential equation for the scalar field perturbations. This work is the first attempt to derive a master equation for black holes in dynamical Chern-Simons gravity using curvature perturbations. The master equations can be numerically integrated to obtain the quasinormal mode spectrum of slowly rotating black holes in this theory, making progress in the study of ringdown in dynamical Chern-Simons gravity. - Open Access
Isospectrality breaking in the Teukolsky formalism
General relativity, though the most successful theory of gravity, has been continuously modified to resolve its incompatibility with quantum mechanics and explain the origin of dark energy or dark matter. One way to test these modified gravity theories is to study the gravitational waves emitted during the ringdown of binary mergers, which consist of quasinormal modes. In several modified gravity theories, the even- and odd-parity gravitational perturbations of non-rotating and slowly rotating black holes have different quasinormal mode frequencies, breaking the isospectrality of general relativity. For black holes with arbitrary spin in modified gravity, there were no avenues to compute quasinormal modes except numerical relativity, until recent extensions of the Teukolsky formalism. In this work, we describe how to use the modified Teukolsky formalism to study isospectrality breaking in modified gravity. We first introduce how definite-parity modes are defined through combinations of Weyl scalars in general relativity, and then, we extend this definition to modified gravity. We then use the eigenvalue perturbation method to show how the degeneracy in quasinormal mode frequencies of different parity is broken in modified gravity. To demonstrate our analysis, we also apply it to some specific modified gravity theories. Our work lays the foundation for studying isospectrality breaking of quasinormal modes in modified gravity for black holes with arbitrary spin.
Open AccessIsospectrality breaking in the Teukolsky formalism
General relativity, though the most successful theory of gravity, has been continuously modified to resolve its incompatibility with quantum mechanics and explain the origin of dark energy or dark matter. One way to test these modified gravity theories is to study the gravitational waves emitted during the ringdown of binary mergers, which consist of quasinormal modes. In several modified gravity theories, the even- and odd-parity gravitational perturbations of non-rotating and slowly rotating black holes have different quasinormal mode frequencies, breaking the isospectrality of general relativity. For black holes with arbitrary spin in modified gravity, there were no avenues to compute quasinormal modes except numerical relativity, until recent extensions of the Teukolsky formalism. In this work, we describe how to use the modified Teukolsky formalism to study isospectrality breaking in modified gravity. We first introduce how definite-parity modes are defined through combinations of Weyl scalars in general relativity, and then, we extend this definition to modified gravity. We then use the eigenvalue perturbation method to show how the degeneracy in quasinormal mode frequencies of different parity is broken in modified gravity. To demonstrate our analysis, we also apply it to some specific modified gravity theories. Our work lays the foundation for studying isospectrality breaking of quasinormal modes in modified gravity for black holes with arbitrary spin.
- 20 September 2023
- Published by American Physical Society (APS) in Physical Review D
- Vol. 108 (6) , 064038
Quantum gravity background in next-generation gravitational wave detectors
We study the effects of geontropic vacuum fluctuations in quantum gravity on next-generation terrestrial gravitational wave detectors. If the Verlinde-Zurek (VZ) effect proposed in Verlinde and Zurek [ Phys. Lett. B 822, 136663 (2021).], as modeled in Zurek [ Phys. Lett. B 826, 136910 (2022); Li et al. Phys. Rev. D 107, 024002 (2023)], appears in the upcoming GQuEST experiment, we show that it will be a large background for astrophysical gravitational wave searches in observatories like Cosmic Explorer and the Einstein Telescope.
- 20 September 2023
- Published by American Physical Society (APS) in Physical Review D
- Vol. 108 (6) , 064038
Quantum gravity background in next-generation gravitational wave detectors
We study the effects of geontropic vacuum fluctuations in quantum gravity on next-generation terrestrial gravitational wave detectors. If the Verlinde-Zurek (VZ) effect proposed in Verlinde and Zurek [ Phys. Lett. B 822, 136663 (2021).], as modeled in Zurek [ Phys. Lett. B 826, 136910 (2022); Li et al. Phys. Rev. D 107, 024002 (2023)], appears in the upcoming GQuEST experiment, we show that it will be a large background for astrophysical gravitational wave searches in observatories like Cosmic Explorer and the Einstein Telescope.