In this paper, we thoroughly explore two crucial aspects of a quantum Schwarzschild black solution within four-dimensional space-time: i) the weak deflection angle, ii) the rigorous greybody factor and, iii) the Dirac quasinormal modes}. Our investigation involves employing the Gauss-Bonnet theorem to precisely compute the deflection angle and establishing its correlation with the Einstein ring. Additionally, we derive the rigorous bounds for greybody factors through the utilization of general bounds for reflection and transmission coefficients in the context of Schrodinger-like one-dimensional potential scattering. We also compute the corresponding Dirac quasinormal modes using the WKB approximation. We reduce the Dirac equation to a Schrodinger-like differential equation and solve it with appropriate boundary conditions to obtain the quasinormal frequencies. To visually underscore the quantum effect, we present figures that illustrate the impact of varying the parameter $r_0$, or more specifically, in terms of the parameter $alpha$. This comprehensive examination enhances our understanding of the quantum characteristics inherent in the Schwarzschild black solution, shedding light on both the deflection angle and greybody factors in a four-dimensional space-time framework.
{"title":"An Effective Model for the Quantum Schwarzschild Black Hole: Weak Deflection Angle, Quasinormal Modes and Bounding of Greybody Factor","authors":"Ángel Rincón, Ali Övgün, Reggie C. Pantig","doi":"arxiv-2409.10930","DOIUrl":"https://doi.org/arxiv-2409.10930","url":null,"abstract":"In this paper, we thoroughly explore two crucial aspects of a quantum\u0000Schwarzschild black solution within four-dimensional space-time: i) the weak\u0000deflection angle, ii) the rigorous greybody factor and, iii) the Dirac\u0000quasinormal modes}. Our investigation involves employing the Gauss-Bonnet\u0000theorem to precisely compute the deflection angle and establishing its\u0000correlation with the Einstein ring. Additionally, we derive the rigorous bounds\u0000for greybody factors through the utilization of general bounds for reflection\u0000and transmission coefficients in the context of Schrodinger-like\u0000one-dimensional potential scattering. We also compute the corresponding Dirac\u0000quasinormal modes using the WKB approximation. We reduce the Dirac equation to\u0000a Schrodinger-like differential equation and solve it with appropriate boundary\u0000conditions to obtain the quasinormal frequencies. To visually underscore the\u0000quantum effect, we present figures that illustrate the impact of varying the\u0000parameter $r_0$, or more specifically, in terms of the parameter $alpha$. This\u0000comprehensive examination enhances our understanding of the quantum\u0000characteristics inherent in the Schwarzschild black solution, shedding light on\u0000both the deflection angle and greybody factors in a four-dimensional space-time\u0000framework.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"47 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142250732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The detection of gravitational waves (GWs) from coalescing compact binaries has become routine with ground-based detectors like LIGO and Virgo. However, beyond standard sources such as binary black holes and neutron stars and neutron star black holes, no exotic sources revealing new physics have been discovered. Detecting ultra-compact objects, such as subsolar mass (SSM) compact objects, offers a promising opportunity to explore diverse astrophysical populations. However, searching for these objects using standard matched-filtering techniques is computationally intensive due to the dense parameter space involved. This increasing computational demand not only challenges current search methodologies but also poses significant obstacles for third-generation (3G) ground-based GW detectors. In the 3G era, signals may last tens of minutes, and detection rates could reach one per minute, requiring efficient search strategies to manage the computational load of long-duration signals. In this paper, we demonstrate a hierarchical search strategy designed to address the challenges of searching for long-duration signals, such as those from SSM compact binaries, and the anticipated issues with 3G detectors. We show that by adopting optimization techniques in a two-stage hierarchical approach, we can efficiently search for the SSM compact object in the current LIGO detectors. Our preliminary results show that conducting matched filtering at a lower frequency of 35 Hz improves the signal-to-noise ratio by 6% and enhances the detection volume by 10-20%, compared to the standard two-detector PyCBC search. This improvement is achieved while reducing computational costs by a factor of 2.5.
{"title":"Hierarchical searches for subsolar-mass binaries and the third-generation gravitational wave detector era","authors":"Kanchan Soni, Alexander H. Nitz","doi":"arxiv-2409.11317","DOIUrl":"https://doi.org/arxiv-2409.11317","url":null,"abstract":"The detection of gravitational waves (GWs) from coalescing compact binaries\u0000has become routine with ground-based detectors like LIGO and Virgo. However,\u0000beyond standard sources such as binary black holes and neutron stars and\u0000neutron star black holes, no exotic sources revealing new physics have been\u0000discovered. Detecting ultra-compact objects, such as subsolar mass (SSM)\u0000compact objects, offers a promising opportunity to explore diverse\u0000astrophysical populations. However, searching for these objects using standard\u0000matched-filtering techniques is computationally intensive due to the dense\u0000parameter space involved. This increasing computational demand not only\u0000challenges current search methodologies but also poses significant obstacles\u0000for third-generation (3G) ground-based GW detectors. In the 3G era, signals may\u0000last tens of minutes, and detection rates could reach one per minute, requiring\u0000efficient search strategies to manage the computational load of long-duration\u0000signals. In this paper, we demonstrate a hierarchical search strategy designed\u0000to address the challenges of searching for long-duration signals, such as those\u0000from SSM compact binaries, and the anticipated issues with 3G detectors. We\u0000show that by adopting optimization techniques in a two-stage hierarchical\u0000approach, we can efficiently search for the SSM compact object in the current\u0000LIGO detectors. Our preliminary results show that conducting matched filtering\u0000at a lower frequency of 35 Hz improves the signal-to-noise ratio by 6% and\u0000enhances the detection volume by 10-20%, compared to the standard two-detector\u0000PyCBC search. This improvement is achieved while reducing computational costs\u0000by a factor of 2.5.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142250720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The generalization of photon spheres by considering the trajectories of massive particles leads to the definition of Massive Particle Surfaces (MPS). These surfaces are built with the trajectories of massive particles, and have a partial umbilicity property. Using the geodesic and Gaussian curvature of the Jacobi metric (a Riemannian metric) we derive a general condition for the existence of a Massive Particle Surface defined for an asymptotically flat spacetime metric. Our results can be applied to the worldlines of charged massive particle surfaces. We provide a simple characterization for timelike and null trajectories using a Riemannian geometric approach. We are able to recover the results for the existence of Light Rings (LR's) and timelike circular orbits (TCO's). We show how an event horizon gets characterized using the curvatures of a Riemannian metric. We discuss several examples, where we derive conditions for the existence of photon sphere and a massive particle surface. We calculate the radius of the photon sphere and the radius of the Innermost Stable Circular Orbits (ISCO).
{"title":"On massive particle surfaces, partial umbilicity and circular orbits","authors":"Boris Bermúdez-Cárdenas, Oscar Lasso Andino","doi":"arxiv-2409.10789","DOIUrl":"https://doi.org/arxiv-2409.10789","url":null,"abstract":"The generalization of photon spheres by considering the trajectories of\u0000massive particles leads to the definition of Massive Particle Surfaces (MPS).\u0000These surfaces are built with the trajectories of massive particles, and have a\u0000partial umbilicity property. Using the geodesic and Gaussian curvature of the\u0000Jacobi metric (a Riemannian metric) we derive a general condition for the\u0000existence of a Massive Particle Surface defined for an asymptotically flat\u0000spacetime metric. Our results can be applied to the worldlines of charged\u0000massive particle surfaces. We provide a simple characterization for timelike\u0000and null trajectories using a Riemannian geometric approach. We are able to\u0000recover the results for the existence of Light Rings (LR's) and timelike\u0000circular orbits (TCO's). We show how an event horizon gets characterized using\u0000the curvatures of a Riemannian metric. We discuss several examples, where we\u0000derive conditions for the existence of photon sphere and a massive particle\u0000surface. We calculate the radius of the photon sphere and the radius of the\u0000Innermost Stable Circular Orbits (ISCO).","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"53 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142250724","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We derive the equations of motion for relativistic elastic membranes, that is, two-dimensional elastic bodies whose internal energy depends only on their stretching, starting from a variational principle. We show how to obtain conserved quantities for the membrane's motion in the presence of spacetime symmetries, determine the membrane's longitudinal and transverse speeds of sound in isotropic states, and compute the coefficients of linear elasticity with respect to the relaxed configuration. We then use this formalism to discuss two physically interesting systems: a rigidly rotating elastic disk, widely discussed in the context of Ehrenfest's paradox, and a Dyson sphere, that is, a spherical membrane in equilibrium in Schwarzschild's spacetime, with the isotropic tangential pressure balancing the gravitational attraction. Surprisingly, although spherically symmetric perturbations of this system are linearly stable, the axi-symmetric dipolar mode is already unstable. This may be taken as a cautionary tale against misconstruing radial stability as true stability.
{"title":"Relativistic elastic membranes: rotating disks and Dyson spheres","authors":"Paulo Mourão, José Natário, Rodrigo Vicente","doi":"arxiv-2409.10602","DOIUrl":"https://doi.org/arxiv-2409.10602","url":null,"abstract":"We derive the equations of motion for relativistic elastic membranes, that\u0000is, two-dimensional elastic bodies whose internal energy depends only on their\u0000stretching, starting from a variational principle. We show how to obtain\u0000conserved quantities for the membrane's motion in the presence of spacetime\u0000symmetries, determine the membrane's longitudinal and transverse speeds of\u0000sound in isotropic states, and compute the coefficients of linear elasticity\u0000with respect to the relaxed configuration. We then use this formalism to\u0000discuss two physically interesting systems: a rigidly rotating elastic disk,\u0000widely discussed in the context of Ehrenfest's paradox, and a Dyson sphere,\u0000that is, a spherical membrane in equilibrium in Schwarzschild's spacetime, with\u0000the isotropic tangential pressure balancing the gravitational attraction.\u0000Surprisingly, although spherically symmetric perturbations of this system are\u0000linearly stable, the axi-symmetric dipolar mode is already unstable. This may\u0000be taken as a cautionary tale against misconstruing radial stability as true\u0000stability.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142250792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Within the isolated horizon formalism, we investigate a static axisymmetric space-time of a black hole influenced by matter in its neighborhood. To illustrate the role of ingredients and assumptions in this formalism, we first show how, in spherical symmetry, the field equations and gauge conditions imply the isolated horizon initial data leading to the Schwarzschild space-time. Then, we construct the initial data for a static axisymmetric isolated horizon representing a deformed black hole. The space-time description in the Bondi-like coordinates is then found as a series expansion in the vicinity of the horizon. To graphically illustrate this construction, we also find a numerical solution for a black hole deformed by a particular analytic model of a thin accretion disk. We also discuss how an accretion disk affects the analytical properties of the horizon geometry.
{"title":"Initial data for a deformed isolated horizon","authors":"Aleš Flandera, David Kofroň, Tomáš Ledvinka","doi":"arxiv-2409.10423","DOIUrl":"https://doi.org/arxiv-2409.10423","url":null,"abstract":"Within the isolated horizon formalism, we investigate a static axisymmetric\u0000space-time of a black hole influenced by matter in its neighborhood. To\u0000illustrate the role of ingredients and assumptions in this formalism, we first\u0000show how, in spherical symmetry, the field equations and gauge conditions imply\u0000the isolated horizon initial data leading to the Schwarzschild space-time.\u0000Then, we construct the initial data for a static axisymmetric isolated horizon\u0000representing a deformed black hole. The space-time description in the\u0000Bondi-like coordinates is then found as a series expansion in the vicinity of\u0000the horizon. To graphically illustrate this construction, we also find a\u0000numerical solution for a black hole deformed by a particular analytic model of\u0000a thin accretion disk. We also discuss how an accretion disk affects the\u0000analytical properties of the horizon geometry.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142250729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
$f(R)$ theories of modified gravity may be compatible with current observations if the deviations from general relativity are sufficiently well screened in dense environments. In recent work [arXiv:2310.19955] we have shown that approximations commonly used to assess whether galaxies are screened, or unscreened, fail to hold in observationally interesting parts of parameter space. One of the assumptions commonly made in these approximations, and more broadly in the study of $f(R)$ models, is that the mass of the scalar mode can be neglected inside a galaxy. In this work we demonstrate that this approximation may fail spectacularly and discuss the implications of this for tests of the theory.
{"title":"Galactic Compton Wavelengths in $f(R)$ Screening Theories","authors":"Bradley March, Clare Burrage, Aneesh P. Naik","doi":"arxiv-2409.10623","DOIUrl":"https://doi.org/arxiv-2409.10623","url":null,"abstract":"$f(R)$ theories of modified gravity may be compatible with current\u0000observations if the deviations from general relativity are sufficiently well\u0000screened in dense environments. In recent work [arXiv:2310.19955] we have shown\u0000that approximations commonly used to assess whether galaxies are screened, or\u0000unscreened, fail to hold in observationally interesting parts of parameter\u0000space. One of the assumptions commonly made in these approximations, and more\u0000broadly in the study of $f(R)$ models, is that the mass of the scalar mode can\u0000be neglected inside a galaxy. In this work we demonstrate that this\u0000approximation may fail spectacularly and discuss the implications of this for\u0000tests of the theory.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"54 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142250728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gravitational waveforms capturing binary's evolution through the early-inspiral phase play a critical role in extracting orbital features that nearly disappear during the late-inspiral and subsequent merger phase due to radiation reaction forces; for instance, the effect of orbital eccentricity. Phenomenological approaches that model compact binary mergers rely heavily on combining inputs from both analytical and numerical approaches to reduce the computational cost of generating templates for data analysis purposes. In a recent work, Chattaraj et al., Phys. Rev. D 106, 124008 (2022) arXiv:2204.02377(gr-qc), we demonstrated construction of a dominant (quadrupole) mode inspiral-merger-ringdown (IMR) model for binary black holes (BBHs) on elliptical orbits. The model was constructed in time-domain and is fully analytical. The current work is an attempt to improve this model by making a few important changes in our approach. The most significant of those involves identifying initial values of orbital parameters with which the inspiral part of the model is evolved. While the ingredients remain the same as in arXiv:2204.02377(gr-qc), resulting waveforms at each stage seem to have improved as a consequence of new considerations proposed here. The updated model is validated also against an independent waveform family resulting overlaps better than $sim 96.5%$ within the calibrated range of binary parameters. Further, we use the prescription of the dominant mode model presented here to provide an alternate (but equivalent) model for the (dominant) quadrupole mode and extend the same to a model including the effect of selected non-quadrupole modes. Finally, while this model assumes non-spinning components, we show that this could also be used for mildly spinning systems with component spins (anti-) aligned w.r.t the orbital angular momentum.
{"title":"An improved IMR model for BBHs on elliptical orbits","authors":"Pratul Manna, Tamal RoyChowdhury, Chandra Kant Mishra","doi":"arxiv-2409.10672","DOIUrl":"https://doi.org/arxiv-2409.10672","url":null,"abstract":"Gravitational waveforms capturing binary's evolution through the\u0000early-inspiral phase play a critical role in extracting orbital features that\u0000nearly disappear during the late-inspiral and subsequent merger phase due to\u0000radiation reaction forces; for instance, the effect of orbital eccentricity.\u0000Phenomenological approaches that model compact binary mergers rely heavily on\u0000combining inputs from both analytical and numerical approaches to reduce the\u0000computational cost of generating templates for data analysis purposes. In a\u0000recent work, Chattaraj et al., Phys. Rev. D 106, 124008 (2022)\u0000arXiv:2204.02377(gr-qc), we demonstrated construction of a dominant\u0000(quadrupole) mode inspiral-merger-ringdown (IMR) model for binary black holes\u0000(BBHs) on elliptical orbits. The model was constructed in time-domain and is\u0000fully analytical. The current work is an attempt to improve this model by\u0000making a few important changes in our approach. The most significant of those\u0000involves identifying initial values of orbital parameters with which the\u0000inspiral part of the model is evolved. While the ingredients remain the same as\u0000in arXiv:2204.02377(gr-qc), resulting waveforms at each stage seem to have\u0000improved as a consequence of new considerations proposed here. The updated\u0000model is validated also against an independent waveform family resulting\u0000overlaps better than $sim 96.5%$ within the calibrated range of binary\u0000parameters. Further, we use the prescription of the dominant mode model\u0000presented here to provide an alternate (but equivalent) model for the\u0000(dominant) quadrupole mode and extend the same to a model including the effect\u0000of selected non-quadrupole modes. Finally, while this model assumes\u0000non-spinning components, we show that this could also be used for mildly\u0000spinning systems with component spins (anti-) aligned w.r.t the orbital angular\u0000momentum.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"100 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142250788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Patrick Chi-Kit Cheong, Antonios Tsokaros, Milton Ruiz, Fabrizio Venturi, Juno Chun Lung Chan, Anson Ka Long Yip, Koji Uryu
We present the first general-relativistic resistive magnetohydrodynamics simulations of self-consistent, rotating neutron stars with mixed poloidal and toroidal magnetic fields. Specifically, we investigate the role of resistivity in the dynamical evolution of neutron stars over a period of up to 100 ms and its effects on their quasi-equilibrium configurations. Our results demonstrate that resistivity can significantly influence the development of magnetohydrodynamic instabilities, resulting in markedly different magnetic field geometries. Additionally, resistivity suppresses the growth of these instabilities, leading to a reduction in the amplitude of emitted gravitational waves. Despite the variations in magnetic field geometries, the ratio of poloidal to toroidal field energies remains consistently 9:1 throughout the simulations, for the models we investigated.
{"title":"General-relativistic resistive-magnetohydrodynamics simulations of self-consistent magnetized rotating neutron stars","authors":"Patrick Chi-Kit Cheong, Antonios Tsokaros, Milton Ruiz, Fabrizio Venturi, Juno Chun Lung Chan, Anson Ka Long Yip, Koji Uryu","doi":"arxiv-2409.10508","DOIUrl":"https://doi.org/arxiv-2409.10508","url":null,"abstract":"We present the first general-relativistic resistive magnetohydrodynamics\u0000simulations of self-consistent, rotating neutron stars with mixed poloidal and\u0000toroidal magnetic fields. Specifically, we investigate the role of resistivity\u0000in the dynamical evolution of neutron stars over a period of up to 100 ms and\u0000its effects on their quasi-equilibrium configurations. Our results demonstrate\u0000that resistivity can significantly influence the development of\u0000magnetohydrodynamic instabilities, resulting in markedly different magnetic\u0000field geometries. Additionally, resistivity suppresses the growth of these\u0000instabilities, leading to a reduction in the amplitude of emitted gravitational\u0000waves. Despite the variations in magnetic field geometries, the ratio of\u0000poloidal to toroidal field energies remains consistently 9:1 throughout the\u0000simulations, for the models we investigated.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"54 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142250735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hengrui Zhu, Jacob Fields, Francesco Zappa, David Radice, James Stone, Alireza Rashti, William Cook, Sebastiano Bernuzzi, Boris Daszuta
We present the numerical relativity module within AthenaK, an open source performance-portable astrophysics code designed for exascale computing applications. This module employs the Z4c formulation to solve the Einstein equations. We demonstrate its accuracy through a series of standard numerical relativity tests, including convergence of the gravitational waveform from binary black hole coalescence. Furthermore, we conduct scaling tests on OLCF Frontier and NERSC Perlmutter, where AthenaK exhibits excellent weak scaling efficiency of 80% on up to 65,536 AMD MI250X GPUs on Frontier (relative to 4 GPUs) and strong scaling efficiencies of 84% and 77% on AMD MI250X and NVIDIA A100 GPUs on Frontier and Perlmutter respectively. Additionally, we observe a significant performance boost, with two orders of magnitude speedup ($gtrsim 200times$) on a GPU compared to a single CPU core, affirming that AthenaK is well-suited for exascale computing, thereby expanding the potential for breakthroughs in numerical relativity research.
{"title":"Performance-Portable Numerical Relativity with AthenaK","authors":"Hengrui Zhu, Jacob Fields, Francesco Zappa, David Radice, James Stone, Alireza Rashti, William Cook, Sebastiano Bernuzzi, Boris Daszuta","doi":"arxiv-2409.10383","DOIUrl":"https://doi.org/arxiv-2409.10383","url":null,"abstract":"We present the numerical relativity module within AthenaK, an open source\u0000performance-portable astrophysics code designed for exascale computing\u0000applications. This module employs the Z4c formulation to solve the Einstein\u0000equations. We demonstrate its accuracy through a series of standard numerical\u0000relativity tests, including convergence of the gravitational waveform from\u0000binary black hole coalescence. Furthermore, we conduct scaling tests on OLCF\u0000Frontier and NERSC Perlmutter, where AthenaK exhibits excellent weak scaling\u0000efficiency of 80% on up to 65,536 AMD MI250X GPUs on Frontier (relative to 4\u0000GPUs) and strong scaling efficiencies of 84% and 77% on AMD MI250X and NVIDIA\u0000A100 GPUs on Frontier and Perlmutter respectively. Additionally, we observe a\u0000significant performance boost, with two orders of magnitude speedup ($gtrsim\u0000200times$) on a GPU compared to a single CPU core, affirming that AthenaK is\u0000well-suited for exascale computing, thereby expanding the potential for\u0000breakthroughs in numerical relativity research.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"52 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142250730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jacob Fields, Hengrui Zhu, David Radice, James M. Stone, William Cook, Sebastiano Bernuzzi, Boris Daszuta
We introduce an extension to the AthenaK code for general-relativistic magnetohydrodynamics (GRMHD) in dynamical spacetimes using a 3+1 conservative Eulerian formulation. Like the fixed-spacetime GRMHD solver, we use standard finite-volume methods to evolve the fluid and a constrained transport scheme to preserve the divergence-free constraint for the magnetic field. We also utilize a first-order flux correction (FOFC) scheme to reduce the need for an artificial atmosphere and optionally enforce a maximum principle to improve robustness. We demonstrate the accuracy of AthenaK using a set of standard tests in flat and curved spacetimes. Using a SANE accretion disk around a Kerr black hole, we compare the new solver to the existing solver for stationary spacetimes using the so-called "HARM-like" formulation. We find that both formulations converge to similar results. We also include the first published binary neutron star (BNS) mergers performed on graphical processing units (GPUs). Thanks to the FOFC scheme, our BNS mergers maintain a relative error of $mathcal{O}(10^{-11})$ or better in baryon mass conservation up to collapse. Finally, we perform scaling tests of AthenaK on OLCF Frontier, where we show excellent weak scaling of $geq 80%$ efficiency up to 32768 GPUs and $74%$ up to 65536 GPUs for a GRMHD problem in dynamical spacetimes with six levels of mesh refinement. AthenaK achieves an order-of-magnitude speedup using GPUs compared to CPUs, demonstrating that it is suitable for performing numerical relativity problems on modern exascale resources.
{"title":"Performance-Portable Binary Neutron Star Mergers with AthenaK","authors":"Jacob Fields, Hengrui Zhu, David Radice, James M. Stone, William Cook, Sebastiano Bernuzzi, Boris Daszuta","doi":"arxiv-2409.10384","DOIUrl":"https://doi.org/arxiv-2409.10384","url":null,"abstract":"We introduce an extension to the AthenaK code for general-relativistic\u0000magnetohydrodynamics (GRMHD) in dynamical spacetimes using a 3+1 conservative\u0000Eulerian formulation. Like the fixed-spacetime GRMHD solver, we use standard\u0000finite-volume methods to evolve the fluid and a constrained transport scheme to\u0000preserve the divergence-free constraint for the magnetic field. We also utilize\u0000a first-order flux correction (FOFC) scheme to reduce the need for an\u0000artificial atmosphere and optionally enforce a maximum principle to improve\u0000robustness. We demonstrate the accuracy of AthenaK using a set of standard\u0000tests in flat and curved spacetimes. Using a SANE accretion disk around a Kerr\u0000black hole, we compare the new solver to the existing solver for stationary\u0000spacetimes using the so-called \"HARM-like\" formulation. We find that both\u0000formulations converge to similar results. We also include the first published\u0000binary neutron star (BNS) mergers performed on graphical processing units\u0000(GPUs). Thanks to the FOFC scheme, our BNS mergers maintain a relative error of\u0000$mathcal{O}(10^{-11})$ or better in baryon mass conservation up to collapse.\u0000Finally, we perform scaling tests of AthenaK on OLCF Frontier, where we show\u0000excellent weak scaling of $geq 80%$ efficiency up to 32768 GPUs and $74%$ up\u0000to 65536 GPUs for a GRMHD problem in dynamical spacetimes with six levels of\u0000mesh refinement. AthenaK achieves an order-of-magnitude speedup using GPUs\u0000compared to CPUs, demonstrating that it is suitable for performing numerical\u0000relativity problems on modern exascale resources.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142250784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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