About

Eanna Flanagan is the Edward L. Nichols Professor of Physics and Professor of Astronomy at Cornell University. His research group focuses on the physics of strong gravitational fields, developing quantitative models of processes involving neutron stars, black holes, and the early Universe. These models are intended to be compared with data from gravitational wave detectors such as LIGO. His research also explores models of the early Universe involving extra dimensions and membranes, as well as models addressing the recent acceleration of the Universe through modifications of general relativity. Flanagan's work encompasses areas such as general relativity, the structure of singularities, radiation reaction of point particles, theoretical astrophysics, gravitational wave astronomy, early Universe cosmology, and extra dimensions including brane world cosmology. His contributions include developing models related to black hole evaporation, gravitational wave phenomena, and the properties of the early Universe, with a focus on understanding the physics of strong gravitational fields.

Research topics

• Mathematical analysis
• Mathematical physics
• Classical mechanics
• Geometry
• Theoretical physics
• Mathematics
• Quantum mechanics
• Physics

Selected publications

• Subregion algebras in classical and quantum gravity

  arXiv (Cornell University) · 2026-01-12

  preprintOpen accessSenior author

  We study the kinematics and dynamics of subregion algebras in classical and perturbative quantum gravity associated with portions of null surfaces such as event horizons and finite causal diamonds. We construct half-sided supertranslation generators by extending subregion phase spaces of the event horizon to include doubled pairs of corner edge modes obtained from splitting the horizon, namely relative boosts and null translations of the respective corners. These edge modes carry a corner symplectic form and give rise to canonical charges generating half-sided boosts and translations. We show that the null translation generator is necessarily two-sided in the complementary translation edge modes. The charges act nontrivially on gravitationally dressed local observables on the horizon, such that the horizon subalgebra naturally takes the form of a crossed product by the associated automorphism group. Quantizing the extended phase space after linearizing around a black hole background, we obtain for each horizon cut a Type II$_{\infty}$ von Neumann algebra equipped with a trace, whose von Neumann entropy coincides with the generalized entropy of that cut. The integrability of the half-sided null translation generator lifts to the existence of a self-adjoint operator that implements null time evolution on the Type II$_\infty$ horizon subalgebras. The area operator is identified as the bulk implementation of the Connes cocycle flow for one-sided observables in excited states. The nesting property of the resulting one-parameter family of horizon subalgebras implies a generalized second law for non-stationary linearized perturbations of Killing horizons. Lastly, we use gravitational half-sided modular inclusion algebras to prove the quantum focusing conjecture in the perturbative quantum gravity regime.

  PublisherDOI

• Conservative and dissipative sectors in a nonlinear scalar model for the gravitational self-force problem

  ArXiv.org · 2026-05-14

  articleOpen access

  When considering how self-interaction affects an object's motion, it can be convenient to decompose the self-force into conservative and dissipative pieces. As a toy model for understanding such decompositions of the gravitational self-force, we consider objects that do not affect the spacetime, but are instead coupled to a nonlinear scalar field. There is then a standard splitting of the first-order scalar self-force into conservative and dissipative components. Multiple criteria can be used to obtain this splitting, all of which imply the same result. However, the implications of these criteria generically differ at higher orders. Demanding that any reasonable conservative sector be Hamiltonian, we identify multiple possible definitions of the conservative second-order self-force. Motivations for these possibilities and their properties are discussed and relevant Hamiltonians are obtained. We assume the existence of a three-point function with certain properties that is a generalization of the Detweiler-Whiting two-point function. These results apply to the two-body problem but are restricted to unbound scattering trajectories, due to infrared divergences that arise for bound orbits.

  PublisherOA PDF

• Conservative and dissipative sectors in a nonlinear scalar model for the gravitational self-force problem

  arXiv (Cornell University) · 2026-05-14

  preprintOpen access

  When considering how self-interaction affects an object's motion, it can be convenient to decompose the self-force into conservative and dissipative pieces. As a toy model for understanding such decompositions of the gravitational self-force, we consider objects that do not affect the spacetime, but are instead coupled to a nonlinear scalar field. There is then a standard splitting of the first-order scalar self-force into conservative and dissipative components. Multiple criteria can be used to obtain this splitting, all of which imply the same result. However, the implications of these criteria generically differ at higher orders. Demanding that any reasonable conservative sector be Hamiltonian, we identify multiple possible definitions of the conservative second-order self-force. Motivations for these possibilities and their properties are discussed and relevant Hamiltonians are obtained. We assume the existence of a three-point function with certain properties that is a generalization of the Detweiler-Whiting two-point function. These results apply to the two-body problem but are restricted to unbound scattering trajectories, due to infrared divergences that arise for bound orbits.

  PublisherDOI

• Subregion algebras in classical and quantum gravity

  ArXiv.org · 2026-01-12

  articleOpen accessSenior author

  We study the kinematics and dynamics of subregion algebras in classical and perturbative quantum gravity associated with portions of null surfaces such as event horizons and finite causal diamonds. We construct half-sided supertranslation generators by extending subregion phase spaces of the event horizon to include doubled pairs of corner edge modes obtained from splitting the horizon, namely relative boosts and null translations of the respective corners. These edge modes carry a corner symplectic form and give rise to canonical charges generating half-sided boosts and translations. We show that the null translation generator is necessarily two-sided in the complementary translation edge modes. The charges act nontrivially on gravitationally dressed local observables on the horizon, such that the horizon subalgebra naturally takes the form of a crossed product by the associated automorphism group. Quantizing the extended phase space after linearizing around a black hole background, we obtain for each horizon cut a Type II$_{\infty}$ von Neumann algebra equipped with a trace, whose von Neumann entropy coincides with the generalized entropy of that cut. The integrability of the half-sided null translation generator lifts to the existence of a self-adjoint operator that implements null time evolution on the Type II$_\infty$ horizon subalgebras. The area operator is identified as the bulk implementation of the Connes cocycle flow for one-sided observables in excited states. The nesting property of the resulting one-parameter family of horizon subalgebras implies a generalized second law for non-stationary linearized perturbations of Killing horizons. Lastly, we use gravitational half-sided modular inclusion algebras to prove the quantum focusing conjecture in the perturbative quantum gravity regime.

  PublisherOA PDF

• Nonlinearly self-interacting extended bodies move as test bodies in effective external fields

  ArXiv.org · 2025-04-16

  preprintOpen accessSenior author

  In electromagnetism, linearized general relativity, and other contexts, previous work has shown that the laws of motion which govern compact, self-interacting bodies can be obtained by applying "Detweiler-Whiting prescriptions" to the laws of motion which govern test bodies. These prescriptions replace any field which appears in a test-body law of motion with a certain effective field which is a quasilocal functional of the physical variables -- a functional that can be interpreted as a regularization procedure in a point-particle limit. We generalize these results, presenting a formalism which allows Detweiler-Whiting prescriptions to be be directly derived for extended bodies, even in nonlinear field theories. If a generating functional with particular properties can be constructed, we find effective linear and angular momenta which evolve via Mathisson-Papapetrou-Dixon equations involving appropriate effective fields. These equations implicitly incorporate all self-force, self-torque, and extended-body effects. Although our main focus is on bodies coupled to nonlinear scalar fields, we also remark on the gravitational case.

  PublisherOA PDFDOI

• Nonlinearly Self-Interacting Extended Bodies Move as Test Bodies in Effective External Fields

  Physical Review Letters · 2025-10-06 · 1 citations

  articleOpen accessSenior author

  In electromagnetism, linearized general relativity, and other contexts, previous work has shown that the laws of motion which govern compact, self-interacting bodies can be obtained by applying "Detweiler-Whiting prescriptions" to the laws of motion that govern test bodies. These prescriptions replace any field that appears in a test-body law of motion with a certain effective field which is a quasilocal functional of the physical variables-a functional that can be interpreted as a regularization procedure in a point-particle limit. We generalize these results, presenting a formalism that allows Detweiler-Whiting prescriptions to be be directly derived for extended bodies, even in nonlinear field theories. If a generating functional with particular properties can be constructed, we find effective linear and angular momenta which evolve via Mathisson-Papapetrou-Dixon equations involving appropriate effective fields. These equations implicitly incorporate all self-force, self-torque, and extended-body effects. Although our main focus is on bodies coupled to nonlinear scalar fields, we also remark on the gravitational case.

  PublisherDOI

• Horizon phase spaces in general relativity

  Journal of High Energy Physics · 2024-07-03 · 12 citations

  articleOpen accessSenior authorCorresponding

  A bstract We derive a prescription for the phase space of general relativity on two intersecting null surfaces using the null initial value formulation. The phase space allows generic smooth initial data, and the corresponding boundary symmetry group is the semidirect product of the group of arbitrary diffeomorphisms of each null boundary which coincide at the corner, with a group of reparameterizations of the null generators. The phase space can be consistently extended by acting with half-sided boosts that generate Weyl shocks along the initial data surfaces. The extended phase space includes the relative boost angle between the null surfaces as part of the initial data. We then apply the Wald-Zoupas framework to compute gravitational charges and fluxes associated with the boundary symmetries. The non-uniqueness in the charges can be reduced to two free parameters by imposing covariance and invariance under rescalings of the null normals. We show that the Wald-Zoupas stationarity criterion cannot be used to eliminate the non-uniqueness. The different choices of parameters correspond to different choices of polarization on the phase space. We also derive the symmetry groups and charges for two subspaces of the phase space, the first obtained by fixing the direction of the normal vectors, and the second by fixing the direction and normalization of the normal vectors. The second symmetry group consists of Carrollian diffeomorphisms on the two boundaries. Finally we specialize to future event horizons by imposing the condition that the area element be non-decreasing and become constant at late times. For perturbations about stationary backgrounds we determine the independent dynamical degrees of freedom by solving the constraint equations along the horizons. We mod out by the degeneracy directions of the presymplectic form, and apply a similar procedure for weak non-degeneracies, to obtain the horizon edge modes and the Poisson structure. We show that the area operator of the black hole generates a shift in the relative boost angle under the Poisson bracket.

  PublisherOA PDFDOI

• Fully nonlinear transformations of the Weyl-Bondi-Metzner-Sachs asymptotic symmetry group

  Journal of High Energy Physics · 2024-03-20 · 5 citations

  articleOpen access1st authorCorresponding

  A bstract The asymptotic symmetry group of general relativity in asymptotically flat spacetimes can be extended from the Bondi-Metzner-Sachs (BMS) group to the generalized BMS (GMBS) group suggested by Campiglia and Laddha, which includes arbitrary diffeomorphisms of the celestial two-sphere. It can be further extended to the Weyl BMS (BMSW) group suggested by Freidel, Oliveri, Pranzetti and Speziale, which includes general conformal transformations. We compute the action of fully nonlinear BMSW transformations on the leading order Bondi-gauge metric functions: specifically, the induced metric, Bondi mass aspect, angular momentum aspect, and shear. These results generalize previous linearized results in the BMSW context by Freidel et al., and also nonlinear results in the BMS context by Chen, Wang, Wang and Yau. The transformation laws will be useful for exploring implications of the BMSW group.

  PublisherOA PDFDOI

• Particle Motion under the Conservative Piece of the Self-Force is Hamiltonian

  Physical Review Letters · 2023-02-01 · 13 citations

  articleOpen accessSenior author

  We consider the motion of a point particle in a stationary spacetime under the influence of a scalar, electromagnetic, or gravitational self-force. We show that the conservative piece of the first-order self-force gives rise to Hamiltonian dynamics, and we derive an explicit expression for the Hamiltonian on phase space. Specialized to the Kerr spacetime, our result generalizes the Hamiltonian function previously obtained by Fujita et al. [Classical Quantum Gravity 34, 134001 (2017).CQGRDG0264-938110.1088/1361-6382/aa7342], which is valid only for nonresonant orbits.

  PublisherOA PDFDOI

• Fully nonlinear transformations of the Weyl-Bondi-Metzner-Sachs asymptotic symmetry group

  arXiv (Cornell University) · 2023-11-06

  preprintOpen access1st authorCorresponding

  The asymptotic symmetry group of general relativity in asymptotically flat spacetimes can be extended from the Bondi-Metzner-Sachs (BMS) group to the generalized BMS (GMBS) group suggested by Campiglia and Laddha, which includes arbitrary diffeomorphisms of the celestial two-sphere. It can be further extended to the Weyl BMS (BMSW) group suggested by Freidel, Oliveri, Pranzetti and Speziale, which includes general conformal transformations. We compute the action of fully nonlinear BMSW transformations on the leading order Bondi-gauge metric functions: specifically, the induced metric, Bondi mass aspect, angular momentum aspect, and shear. These results generalize previous linearized results in the BMSW context by Freidel et al., and also nonlinear results in the BMS context by Chen, Wang, Wang and Yau. The transformation laws will be useful for exploring implications of the BMSW group.

  PublisherOA PDFDOI

Recent grants

• Gravitation Physics and Relativistic Astrophysics

  NSF · $445k · 2014–2017

• Gravitation physics and relativistic astrophysics

  NSF · $420k · 2008–2011

• Gravitation Physics and Relativistic Astrophysics

  NSF · $480k · 2021–2024

• Gravitation physics and relativistic astrophysics

  NSF · $340k · 2005–2008

• Gravitation Physics and Relativistic Astrophysics

  NSF · $480k · 2011–2015

Frequent coauthors

• J. D. E. Creighton

  24 shared

• Curt Cutler

  Jet Propulsion Laboratory

  19 shared

• B. Allen

  19 shared

• Ira Wasserman

  18 shared

• M. Smith

  17 shared

• Tanja Hinderer

  Utrecht University

  17 shared

• A. M. Sintes

  Universitat de les Illes Balears

  15 shared

• A. Weidner

  Max Planck Institute for Gravitational Physics

  15 shared

Labs

• Eanna Flanagan Research GroupPI

Awards & honors

• Xanthopoulos prize in gravitation (2004)
• Fellow of the American Physical Society (2008)
• Fellow of the International Society on General Relativity an…
• Alfred P. Sloan fellow (1997-99)
• Radcliffe fellow (2002-03)