107 citations · 686 across the 23 of their papers we have counts for
23 papers
Nonlinear evolution of the ergoregion instability: Turbulence, bursts of radiation, and black hole formation
Nils Siemonsen, William E. East
Spacetimes with an ergoregion that is not connected to a horizon are linearly unstable. While the linear regime has been studied in a number of settings, little is known about the…
Implications of GW241011 for rotating exotic compact objects
N. V. Krishnendu, Tamara Evstafyeva, Aditya Vijaykumar +17
A number of theoretical proposals have been made for horizonless compact objects with masses and spins similar to those of black holes. While gravitational wave signatures from the…
Assessing the stability of ultracompact spinning boson stars with nonlinear evolutions
Tamara Evstafyeva, Nils Siemonsen, William E. East
We reinvestigate the stability properties of ultracompact spinning boson stars with a stable light ring using fully nonlinear 3+1 and 2+1 numerical relativity simulations and two d…
Ultralight boson constraints from gravitational wave observations of spinning binary black holes
P. S. Aswathi, William E. East, Nils Siemonsen +2
In the presence of an ultralight scalar or vector boson, a spinning black hole will be spun down through the superradiant instability. We use spin measurements from gravitational w…
Black hole mimickers: from theory to observation
Cosimo Bambi, Ramy Brustein, Vitor Cardoso +16
The black hole paradigm, while remarkably successful, raises fundamental questions-both classical and quantum-about the nature of spacetime, horizons, and singularities. Black hole…
Periodic Cosmic String Formation and Dynamics
Michael A. Fedderke, Junwu Huang, Nils Siemonsen
We study string formation and dynamics in a scalar field theory with a global symmetry. If a scalar field is initially displaced from the minimum of a wine-bottle potent…
Search for continuous gravitational wave signals from luminous dark photon superradiance clouds with LVK O3 observations
Lorenzo Mirasola, Cristina Mondino, Francesco Amicucci +10
Superradiance clouds of kinetically-mixed dark photons around spinning black holes can produce observable multi-messenger electromagnetic and gravitational wave signals. The cloud…
Methodology for constraining ultralight vector bosons with gravitational wave searches targeting merger remnant black holes
Dana Jones, Nils Siemonsen, Ling Sun +4
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 ultralig…
Self-Gravity Effects of Ultralight Boson Clouds Formed by Black Hole Superradiance
Taillte May, William E. East, Nils Siemonsen
Oscillating clouds of ultralight bosons can grow around spinning black holes through superradiance, extracting energy and angular momentum, and eventually dissipating through gravi…
Nonlinear treatment of a black hole mimicker ringdown
Nils Siemonsen
We perform the first nonlinear and self-consistent study of the merger and ringdown of a black hole mimicking object with stable light rings. To that end, we numerically solve the…
Instability and backreaction of massive spin-2 fields around black holes
William E. East, Nils Siemonsen
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…
Generic initial data for binary boson stars
Nils Siemonsen, William E. East
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…
Methods and prospects for gravitational wave searches targeting ultralight vector boson clouds around known black holes
Dana Jones, Ling Sun, Nils Siemonsen +3
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 t…
Binary boson stars: Merger dynamics and formation of rotating remnant stars
Nils Siemonsen, William E. East
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…
Dark photon superradiance: Electrodynamics and multimessenger signals
Nils Siemonsen, Cristina Mondino, Daniel Egana-Ugrinovic +3
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 resulti…
SuperRad: Modeling the black hole superradiance gravitational waveform
Nils Siemonsen, Taillte May, William E. East
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 wou…
Dark Matter In Extreme Astrophysical Environments
Masha Baryakhtar, Regina Caputo, Djuna Croon +37
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…
Post-Newtonian Waveforms from Spinning Scattering Amplitudes
Yilber Fabian Bautista, Nils Siemonsen
We derive the classical gravitational radiation from an aligned spin binary black hole on \textit{closed} orbits, using a dictionary built from the 5-point QFT scattering amplitude…
Stability of rotating scalar boson stars with nonlinear interactions
Nils Siemonsen, William E. East
We study the stability of rotating scalar boson stars, comparing those made from a simple massive complex scalar (referred to as mini boson stars), to those with several different…
Modeling and searching for a stochastic gravitational-wave background from ultralight vector bosons
Leo Tsukada, Richard Brito, William E. East +1
Ultralight bosons, which are predicted in a variety of beyond-Standard-Model scenarios as dark-matter candidates, can trigger the superradiant instability around spinning black hol…
Gravitational wave signatures of ultralight vector bosons from black hole superradiance
Nils Siemonsen, William E. East
In the presence of an ultralight bosonic field, spinning black holes are unstable to superradiance. The rotational energy of the black hole is converted into a non-axisymmetric, os…
Test black holes, scattering amplitudes and perturbations of Kerr spacetime
Nils Siemonsen, Justin Vines
It has been suggested that amplitudes for quantum higher-spin massive particles exchanging gravitons lead, via a classical limit, to results for scattering of spinning black holes…
Gravitational waves from spinning binary black holes at the leading post-Newtonian orders at all orders in spin
Nils Siemonsen, Jan Steinhoff, Justin Vines
We determine the binding energy, the total gravitational wave energy flux, and the gravitational wave modes for a binary of rapidly spinning black holes, working in linearized grav…