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Defining eccentricity for gravitational wave astronomy

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arXiv 2023年

作者： Shaikh, Md Arif Varma, Vijay Pfeiffer, Harald P. Ramos-Buades, Antoni van de Meent, Maarten Department of Physics and Astronomy Seoul National University Seoul08826 Korea Republic of International Centre for Theoretical Sciences Tata Institute of Fundamental Research Bangalore560089 India PotsdamD-14476 Germany Department of Mathematics Center for Scientific Computing and Data Science Research University of Massachusetts DartmouthMA02747 United States Niels Bohr International Academy Niels Bohr Institute Blegdamsvej 17 Copenhagen2100 Denmark

Eccentric compact binary mergers are significant scientific targets for current and future gravitational wave observatories. To detect and analyze eccentric signals, there is an increasing effort to develop waveform models, numerical relativity simulations, and parameter estimation frameworks for eccentric binaries. Unfortunately, current models and simulations use different internal parameterisations of eccentricity in the absence of a unique natural definition of eccentricity in general relativity, which can result in incompatible eccentricity measurements. In this paper, we adopt a standardized definition of eccentricity and mean anomaly based solely on waveform quantities, and make our implementation publicly available through an easy-to-use Python package, gw_eccentricity. This definition is free of gauge ambiguities, has the correct Newtonian limit, and can be applied as a postprocessing step when comparing eccentricity measurements from different models. This standardization puts all models and simulations on the same footing and enables direct comparisons between eccentricity estimates from gravitational wave observations and astrophysical predictions. We demonstrate the applicability of this definition and the robustness of our implementation for waveforms of different origins, including post-Newtonian theory, effective one body, extreme mass ratio inspirals, and numerical relativity simulations. We focus on binaries without spin-precession in this work, but possible generalizations to spin-precessing binaries are discussed. © 2023, CC BY.

关键词： Gravity waves

Space-time collocation method: Loop quantum hamiltonian constraints

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arXiv 2020年

作者： Yonika, A. Heryudono, A. Khanna, G. Department of Physics Center for Scientific Computing and Visualization Research University of Massachusetts Dartmouth 285 Old Westport Road North DartmouthMA02747 United States Department of Mathematics Center for Scientific Computing and Visualization Research University of Massachusetts Dartmouth 285 Old Westport Road North DartmouthMA02747 United States

A space-time collocation method (STCM) using asymptotically-constant basis functions is proposed and applied to the quantum Hamiltonian constraint for a loop-quantized treatment of the Schwarzschild interior. Canonically, these descriptions take the form of a partial-difference equation (PDE). The space-time collocation approach presents a computationally efficient, convergent, and easily parallelizable method for solving this class of equations, which is the main novelty of this study. Results of the numerical simulations will demonstrate the benefit from a parallel computing approach;and show general exibility of the framework to handle arbitrarily-sized domains. Computed solutions will be compared, when applicable, to a solution computed in the conventional method via iteratively stepping through a predefined grid of discrete values, computing the solution via a recursive relationship. Copyright © 2020, The Authors. All rights reserved.

关键词： Gravitation

Modeling the BMS transformation induced by a binary black hole merger

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arXiv 2025年

作者： Da Re, Guido Mitman, Keefe Stein, Leo C. Scheel, Mark A. Teukolsky, Saul A. Sun, Dongze Boyle, Michael Deppe, Nils Field, Scott E. Kidder, Lawrence E. Moxon, Jordan Nelli, Kyle C. Throwe, William Varma, Vijay Vu, Nils L. Theoretical Astrophysics 350-17 California Institute of Technology PasadenaCA91125 United States Cornell Center for Astrophysics and Planetary Science Cornell University IthacaNY14853 United States Department of Physics and Astronomy University of Mississippi UniversityMS38677 United States Laboratory for Elementary Particle Physics Cornell University IthacaNY14853 United States Department of Physics Cornell University IthacaNY14853 United States Department of Mathematics Center for Scientific Computing and Data Science Research University of Massachusetts DartmouthMA02747 United States

Understanding the characteristics of the remnant black hole formed in a binary black hole merger is crucial for conducting gravitational wave astronomy. Typically, models of remnant black holes provide information about their mass, spin, and kick velocity. However, other information related to the supertranslation symmetries of the BMS group, such as the memory effect, is also important for characterizing the final state of the system. In this work, we build a model of the BMS transformation that maps a binary black hole’s inspiral frame to the remnant black hole’s canonical rest frame. Training data for this model are created using high-precision numerical relativity simulations of quasi-circular systems with mass ratios q ≤ 8 and spins parallel to the orbital angular momentum with magnitudes χ1, χ2 ≤ 0.8. We use Gaussian Process Regression to model the BMS transformations over the three-dimensional parameter space (q, χz1, χz2). The physics captured by this model is strictly non-perturbative and cannot be obtained from post-Newtonian approximations alone, as it requires knowledge of the strong nonlinear effects that are sourced during the merger. Apart from providing the first model of the supertranslation induced by a binary black hole merger, we also find that the kick velocities predicted using Cauchy-characteristic evolution waveforms are, on average, ∼ 5% larger than the ones obtained from extrapolated waveforms. Our work has broad implications for improving gravitational wave models and studying the large-scale impact of memory, such as on the cosmological background. The fits produced in this work are available through the Python package surfinBH under the name NRSur3dq8BMSRemnant. © 2025, CC BY.

关键词： Relativity

Non-Axisymmetric Gravitational "Hair" for Extremal Black Holes

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arXiv 2024年

作者： Bishoyi, Som Dev Sabharwal, Subir Khanna, Gaurav Department of Mathematics University of Massachusetts Dartmouth 285 Old Westport Rd. North DartmouthMA02747 United States Center for Scientific Computing & Data-Science Research University of Massachusetts Dartmouth 285 Old Westport Rd. North DartmouthMA02747 United States Center for Computational Research University of Rhode Island KingstonRI02881 United States Department of Physics University of Rhode Island KingstonRI02881 United States Department of Physics University of Massachusetts Dartmouth 285 Old Westport Rd. North DartmouthMA02747 United States

Various generalizations of the scalar, axisymmetric Aretakis "horizon hair" for extremal black holes have recently appeared in the literature. In this paper, we present an expression for a non-axisymmetric Aretakis gravitational charge and its potentially observable imprint at a finite distance from the horizon (Ori-coefficient) in extremal Kerr black hole backgrounds. We offer strong and robust numerical evidence for the existence of this hair and its properties. Specifically, we consider the time evolution of horizon penetrating, quadrupolar and (subdominant) octupolar gravitational perturbations with compact support on extremal Kerr (EK) spacetime. We do this by numerically solving the Teukolsky equation and determining the Aretakis charge values on the horizon and at a finite distance from the black hole. Copyright © 2024, The Authors. All rights reserved.

关键词： Black holes

Adding higher-order spherical harmonics in non-spinning eccentric binary black hole merger waveform models

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arXiv 2024年

作者： Islam, Tousif Khanna, Gaurav Field, Scott E. Kavli Institute for Theoretical Physics University of California Santa Barbara Kohn Hall Lagoon Rd Santa BarbaraCA93106 United States Theoretical AstroPhysics Including Relativity and Cosmology California Institute of Technology PasadenaCA United States Department of Physics Center for Computational Research University of Rhode Island KingstonRI02881 United States Department of Physics University of Massachusetts DartmouthMA02747 United States Center for Scientific Computing and Data Science Research University of Massachusetts DartmouthMA02747 United States Department of Mathematics University of Massachusetts DartmouthMA02747 United States

gwNRHME is a recently developed framework that seamlessly converts a multi-modal (i.e with several spherical harmonic modes) quasi-circular waveform into multi-modal eccentric waveform if the quadrupolar eccentric waveform is known. Here, we employ the gwNRHME framework to combine a multi-modal quasi-circular waveform model NRHybSur3dq8 and quadrupolar non-spinning eccentric waveform model EccentricIMR to construct multi-modal non-spinning eccentric model NRHybSur3dq8-gwNRHME. Using a total of 35 eccentric numerical relativity (NR) simulations obtained from the SXS and RIT catalogs, we demonstrate that NRHybSur3dq8-gwNRHME model predictions agree well with NR (with typical relative L2 errors of ∼ 0.01 for the dominant quadrupolar mode) for mass ratios 1 ≤ q ≤ 4 and eccentricities up to ∼ 0.2 measured about 10 cycles before the merger. To demonstrate the modularity of the gwNRHME framework, we further combine EccentricIMR with BHPTNRSur1dq1e4 model and develop a non-spinning eccentric models named BHPTNRSur1dq1e4-gwNRHME. Finally, we develop a different variant of these models by replacing EccentricIMR with EccentricTD. Both the gwNRHME framework and associated models are available through the gwModels package. Copyright © 2024, The Authors. All rights reserved.

关键词： Spheres

Scalable Multiscale-Spectral Gfem with an Application to Composite Aero-Structures

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SSRN

SSRN 2023年

作者： Bénézech, Jean Seelinger, Linus Bastian, Peter Butler, Richard Dodwell, Timothy Ma, Chupeng Scheichl, Robert Centre for Integrated Materials Processes and Structures University of Bath BathBA2 7AY United Kingdom Institute for Applied Mathematics Interdisciplinary Center for Scientific Computing Heidelberg University Heidelberg Germany Institute of Data Science and AI University of Exeter UK & digiLab Exeter Exeter United Kingdom Department of Mathematical Sciences University of Bath Bath United Kingdom Institute of Scientific Research Great Bay University Dongguan China

In this paper, the first large-scale application of multiscale-spectral generalized finite element methods (MS-GFEM) to composite aero-structures is presented. The crucial novelty lies in the introduction of A-harmonicity in the local approximation spaces, which in contrast to [Babuska, Lipton,Multiscale Model. Simul.9,[Babuska, Lipton, Multiscale Model. Simul. 9, 2011] is enforced more efficiently via a constraint in the local eigenproblems. This significant modification leads to excellent approximation properties, which turn out to be essential to capture accurately material strains and stresses with a low dimensional approximation space, hence maximising model order reduction. The implementation of the framework in the DUNE software package, as well as a detailed description of all components of the method are presented and exemplified on a composite laminated beam under compressive loading. The excellent parallel scalability of the method, as well as its superior performance compared to the related, previously introduced GenEO method are demonstrated on two realistic application cases, including a C-shaped wing spar with complex geometry. Further, by allowing low-cost approximate solves for closely related models or geometries this efficient, novel technology provides the basis for future applications in optimisation or uncertainty quantification on challenging problems in composite aero-structures. © 2023, The Authors. All rights reserved.

关键词： Finite element method

The Parallel Compact Object CALculator: An Efficient General Relativistic Initial Data Solver for Compact Objects

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arXiv 2023年

作者： Boukas, Lambros Tsokaros, Antonios Uryū, Kōji LAB Scientific Computing Inc. MiamiFL33176 United States Department of Physics University of Illinois at Urbana-Champaign UrbanaIL61801 United States National Center for Supercomputing Applications University of Illinois at Urbana-Champaign UrbanaIL61801 United States Research Center for Astronomy and Applied Mathematics Academy of Athens Athens11527 Greece University of the Ryukyus Department of Physics Senbaru Okinawa Nishihara903-0213 Japan

Every numerical general relativistic investigation starts from the solution of the initial value equations at a given time. Astrophysically relevant initial values for different systems lead to distinct set of equations that obey specific assumptions tied to the particular problem. Therefore a robust and efficient solver for a variety of strongly gravitating sources is needed. In this work we present the OpenMP version of the Compact Object CALculator (COCAL) on shared memory processors. We performed extensive profiling of the core COCAL modules in order to identify bottlenecks in efficiency which we addressed. Using modest resources, the new parallel code achieves speedups approximately one order of magnitude relative to the original serial COCAL code, which is crucial for parameter studies of computationally expensive systems, such as magnetized neutron stars, as well as its further development towards more realistic scenarios. As a novel example of our new code we compute a binary quark system where each companion has a dimensionless spin of 0.43 aligned with the orbital angular momentum. © 2023, CC BY.

关键词： Application programming interfaces (API)

GW190521: Tracing imprints of spin-precession on the most massive black hole binary

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Physical Review D 2024年第2期109卷 024024-024024页

作者： Simona J. Miller Maximiliano Isi Katerina Chatziioannou Vijay Varma Ilya Mandel Department of Physics California Institute of Technology Pasadena California 91125 USA LIGO Laboratory California Institute of Technology Pasadena California 91125 USA Center for Computational Astrophysics Flatiron Institute New York New York 10010 USA Department of Mathematics Center for Scientific Computing and Data Science Research University of Massachusetts Dartmouth Massachusetts 02747 USA Max Planck Institute for Gravitational Physics (Albert Einstein Institute) D-14476 Potsdam Germany School of Physics and Astronomy Monash University Clayton Victoria 3800 Australia OzGrav: The ARC Centre of Excellence for Gravitational Wave Discovery Clayton Victoria 3800 Australia

GW190521 is a remarkable gravitational-wave signal on multiple fronts: its source is the most massive black hole binary identified to date and could have spins misaligned with its orbit, leading to spin-induced precession; an astrophysically consequential property linked to the binary’s origin. However, due to its large mass, GW190521 was only observed during its final 3–4 cycles, making precession constraints puzzling and giving rise to alternative interpretations, such as eccentricity. Motivated by these complications, we trace the observational imprints of precession on GW190521 by dissecting the data with a novel time domain technique, allowing us to explore the morphology and interplay of the few observed cycles. We find that precession inference hinges on a quiet portion of the pre-merger data that is suppressed relative to the merger ringdown. Neither premerger nor postmerger data alone are the sole driver of inference, but rather their combination; in the quasicircular scenario, precession emerges as a mechanism to accommodate the lack of a stronger premerger signal in light of the observed postmerger. In terms of source dynamics, the premerger suppression arises from a tilting of the binary with respect to the observer. Establishing such a consistent picture between the source dynamics and the observed data is crucial for characterizing the growing number of massive binary observations and bolstering the robustness of ensuing astrophysical claims.

关键词： Gravitational wave detection Gravitational wave sources Gravitational waves Astronomical black holes Classical black holes Spin Numerical simulations in gravitation & astrophysics

An observational signature for extremal black holes

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arXiv 2023年

作者： Aretakis, Stefanos Khanna, Gaurav Sabharwal, Subir Department of Mathematics University of Toronto 40 St George Street TorontoON Canada Department of Physics University of Rhode Island KingstonRI02881 United States Department of Physics University of Massachusetts Dartmouth 285 Old Westport Rd. North DartmouthMA02747 United States Center for Scientific Computing & Data-Science Research University of Massachusetts Dartmouth 285 Old Westport Rd. North DartmouthMA02747 United States Center for Computational Research University of Rhode Island KingstonRI02881 United States

We consider scalar perturbations of the Reissner-Nordström family and the Kerr family. We derive a characteristic expression of the radiation field, at any given unit solid angle of future null infinity, and numerically show that its amplitude gets excited only in the extremal case. Our work, therefore, identifies an observational signature for extremal black holes. Moreover, we show that the source of the excitation is the extremal horizon instability and its magnitude is exactly equal to the conserved horizon charge. Copyright © 2023, The Authors. All rights reserved.

关键词： Black holes