William E. East
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View article: Nonlinear evolution of the spin-2 black hole superradiant instability
Nonlinear evolution of the spin-2 black hole superradiant instability Open
Massive spin-2 fields, which arise in proposed extensions of the standard model of particle physics and general relativity, give rise to a superradiant instability around spinning black holes. We study the nonlinear evolution of this insta…
View article: Search for continuous gravitational wave signals from luminous dark photon superradiance clouds with LVK O3 observations
Search for continuous gravitational wave signals from luminous dark photon superradiance clouds with LVK O3 observations Open
Superradiance clouds of kinetically mixed dark photons around spinning black holes can produce observable multimessenger electromagnetic and gravitational wave signals. The cloud generates electric fields of up to a teravolt-per-meter, whi…
View article: Search for continuous gravitational wave signals from luminous dark photon superradiance clouds with LVK O3 observations
Search for continuous gravitational wave signals from luminous dark photon superradiance clouds with LVK O3 observations Open
Superradiance clouds of kinetically-mixed dark photons around spinning black holes can produce observable multi-messenger electromagnetic and gravitational wave signals. The cloud generates electric fields of up to a Teravolt-per-meter, wh…
View article: Methodology for constraining ultralight vector bosons with gravitational wave searches targeting merger remnant black holes
Methodology for constraining ultralight vector bosons with gravitational wave searches targeting merger remnant black holes Open
Ultralight bosons are a hypothetical class of particles predicted under various extensions of Standard Model physics. As a result of the superradiance mechanism, we expect ultralight bosons, should they exist in certain mass ranges, to for…
View article: Self-Gravity Effects of Ultralight Boson Clouds Formed by Black Hole Superradiance
Self-Gravity Effects of Ultralight Boson Clouds Formed by Black Hole Superradiance Open
Oscillating clouds of ultralight bosons can grow around spinning black holes through superradiance, extracting energy and angular momentum, and eventually dissipating through gravitational radiation. Gravitational wave detectors like LIGO,…
View article: Black hole-neutron star mergers in Einstein-scalar-Gauss-Bonnet gravity
Black hole-neutron star mergers in Einstein-scalar-Gauss-Bonnet gravity Open
Gravitational wave observations of black hole-neutron star binaries, particularly those where the black hole has a lower mass compared to other observed systems, have the potential to place strong constraints on modifications to general re…
View article: Nonlinear studies of modifications to general relativity: Comparing different approaches
Nonlinear studies of modifications to general relativity: Comparing different approaches Open
Studying the dynamical, nonlinear regime of modified theories of gravity remains a theoretical challenge that limits our ability to test general relativity. Here we consider two generally applicable, but approximate, methods for treating m…
View article: Black hole-neutron star mergers in Einstein-scalar-Gauss-Bonnet gravity
Black hole-neutron star mergers in Einstein-scalar-Gauss-Bonnet gravity Open
Gravitational wave observations of black hole-neutron star binaries, particularly those where the black hole has a lower mass compared to other observed systems, have the potential to place strong constraints on modifications to general re…
View article: Nonlinear effect of absorption on the ringdown of a spinning black hole
Nonlinear effect of absorption on the ringdown of a spinning black hole Open
The ringdown gravitational wave signal arising e.g., in the final stage of a black hole binary merger, contains important information about the properties of the remnant, and can potentially be used to perform clean tests of general relati…
View article: Nonlinear studies of modifications to general relativity: Comparing different approaches
Nonlinear studies of modifications to general relativity: Comparing different approaches Open
Studying the dynamical, nonlinear regime of modified theories of gravity remains a theoretical challenge that limits our ability to test general relativity. Here we consider two generally applicable, but approximate methods for treating mo…
View article: Starting inflation from inhomogeneous initial conditions with momentum
Starting inflation from inhomogeneous initial conditions with momentum Open
We investigate the circumstances under which cosmic inflation can arise from very inhomogeneous initial conditions using numerical relativity simulations. Previous studies have not considered cases with non-zero momentum density due to tec…
View article: Instability and backreaction of massive spin-2 fields around black holes
Instability and backreaction of massive spin-2 fields around black holes Open
A massive spin-2 field can grow unstably around a black hole, giving rise to a potential probe of the existence of such fields. In this work, we use time-domain evolutions to study such instabilities. Considering the linear regime by solvi…
View article: Generic initial data for binary boson stars
Generic initial data for binary boson stars Open
Binary boson stars can be used to model the nonlinear dynamics and gravitational wave signals of merging ultracompact, but horizonless, objects. However, doing so requires initial data satisfying the Hamiltonian and momentum constraints of…
View article: Methods and prospects for gravitational wave searches targeting ultralight vector boson clouds around known black holes
Methods and prospects for gravitational wave searches targeting ultralight vector boson clouds around known black holes Open
Ultralight bosons are predicted in many extensions to the Standard Model and are popular dark matter candidates. The black hole superradiance mechanism allows for these particles to be probed using only their gravitational interaction. In …
View article: Dark photon superradiance: Electrodynamics and multimessenger signals
Dark photon superradiance: Electrodynamics and multimessenger signals Open
We study the electrodynamics of a kinetically mixed dark photon cloud that forms through superradiance around a spinning black hole, and design strategies to search for the resulting multimessenger signals. A dark photon superradiance clou…
View article: Binary boson stars: Merger dynamics and formation of rotating remnant stars
Binary boson stars: Merger dynamics and formation of rotating remnant stars Open
Scalar boson stars have attracted attention as simple models for exploring the nonlinear dynamics of a large class of ultra compact and black hole mimicking objects. Here, we study the impact of interactions in the scalar matter making up …
View article: Nonlinear studies of binary black hole mergers in Einstein-scalar-Gauss-Bonnet gravity
Nonlinear studies of binary black hole mergers in Einstein-scalar-Gauss-Bonnet gravity Open
We study the nonlinear dynamics of binary black hole systems with scalar charge by numerically evolving the full equations of motion for shift-symmetric Einstein scalar Gauss-Bonnet gravity. We consider quasi-circular binaries with differe…
View article: Dark photon superradiance: Electrodynamics and multimessenger signals
Dark photon superradiance: Electrodynamics and multimessenger signals Open
We study the electrodynamics of a kinetically mixed dark photon cloud that forms through superradiance around a spinning black hole, and design strategies to search for the resulting multimessenger signals. A dark photon superradiance clou…
View article: Dark photon vortex formation and dynamics
Dark photon vortex formation and dynamics Open
A bstract We study the formation and evolution of vortices in U(1) dark photon dark matter and dark photon clouds that arise through black hole superradiance. We show how the production of both longitudinal mode and transverse mode dark ph…
View article: Starting inflation from inhomogeneous initial conditions with momentum
Starting inflation from inhomogeneous initial conditions with momentum Open
We investigate the circumstances under which cosmic inflation can arise from very inhomogeneous initial conditions using numerical relativity simulations. Previous studies have not considered cases with non-zero momentum density due to tec…
View article: SuperRad: Modeling the black hole superradiance gravitational waveform
SuperRad: Modeling the black hole superradiance gravitational waveform Open
Gravitational signatures of black hole superradiance are a unique probe of ultralight particles that are weakly-coupled to ordinary matter. The existence of an ultralight boson would lead spinning black holes with size comparable to the Co…
View article: Vortex String Formation in Black Hole Superradiance of a Dark Photon with the Higgs Mechanism
Vortex String Formation in Black Hole Superradiance of a Dark Photon with the Higgs Mechanism Open
Black hole superradiance, which only relies on gravitational interactions, can provide a powerful probe of the existence of ultralight bosons that are weakly coupled to ordinary matter. However, as a boson cloud grows through superradiance…
View article: Evolution of black holes through a nonsingular cosmological bounce
Evolution of black holes through a nonsingular cosmological bounce Open
We study the classical dynamics of black holes during a nonsingular cosmological bounce. Taking a simple model of a nonsingular bouncing cosmology driven by the combination of a ghost and ordinary scalar field, we use nonlinear evolutions …
View article: Binary neutron star mergers in Einstein-scalar-Gauss-Bonnet gravity
Binary neutron star mergers in Einstein-scalar-Gauss-Bonnet gravity Open
Binary neutron star mergers, which can lead to less massive black holes relative to other known astrophysical channels, have the potential to probe modifications to general relativity that arise at smaller curvature scales compared to more…
View article: Dark photon vortex formation and dynamics
Dark photon vortex formation and dynamics Open
We study the formation and evolution of vortices in $U(1)$ dark photon dark matter and dark photon clouds that arise through black hole superradiance. We show how the production of both longitudinal mode and transverse mode dark photon dar…
View article: Using machine learning to parametrize postmerger signals from binary neutron stars
Using machine learning to parametrize postmerger signals from binary neutron stars Open
There is growing interest in the detection and characterization of gravitational waves from postmerger oscillations of binary neutron stars. These signals contain information about the nature of the remnant and the high-density and out-of-…
View article: Vortex String Formation in Black Hole Superradiance of a Dark Photon with the Higgs Mechanism
Vortex String Formation in Black Hole Superradiance of a Dark Photon with the Higgs Mechanism Open
Black hole superradiance, which only relies on gravitational interactions, can provide a powerful probe of the existence of ultralight bosons that are weakly coupled to ordinary matter. However, as a boson cloud grows through superradiance…
View article: Nonlinear effects in the black hole ringdown: Absorption-induced mode excitation
Nonlinear effects in the black hole ringdown: Absorption-induced mode excitation Open
Gravitational-wave observations of black hole ringdowns are commonly used to\ncharacterize binary merger remnants and to test general relativity. These\nanalyses assume linear black hole perturbation theory, in particular that the\nringdow…
View article: Dark Matter In Extreme Astrophysical Environments
Dark Matter In Extreme Astrophysical Environments Open
Exploring dark matter via observations of extreme astrophysical environments -- defined here as heavy compact objects such as white dwarfs, neutron stars, and black holes, as well as supernovae and compact object merger events -- has been …
View article: The Next Generation Global Gravitational Wave Observatory: The Science Book
The Next Generation Global Gravitational Wave Observatory: The Science Book Open
The next generation of ground-based gravitational-wave detectors will observe coalescences of black holes and neutron stars throughout the cosmos, thousands of them with exceptional fidelity. The Science Book is the result of a 3-year effo…