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Author: Francesco Zappa
Publisher:
ISBN:
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Languages : de
Pages : 0
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Book Description
Numerical relativity (NR) simulations are crucial for studying the coalescence of compact binaries. Based on NR data, we produce a model for the mass and spin of the remnant black hole (BH) for the coalescence of black hole-neutron star systems, discussing its crucial role in gravitational wave (GW) modeling and in the parameter estimation of the two signals GW200105 and GW200115. In the context of binary neutron star merger simulations, we perform the first systematic study comparing results obtained with various neutrino treatments, the presence of turbulent viscosity and different grid resolutions. We find that the time of BH formation after merger is heavily affected by grid resolution and turbulent viscosity. An early BH formation limits matter ejection from the accretion disc, as the BH swallows a significant portion of it. Our results indicate that more reliable kilonova light curves are obtained only if the various ejecta components are present. Moreover, robust r-process nucleosynthesis yields require inclusion of both neutrino emission and reabsorption in simulations. Advanced neutrino schemes and turbulent viscosity in simulations resolved beyond current standards appear necessary for reliable astrophysical predictions. To carry out computationally demanding simulations of growing complexity, next-generation NR codes that can efficiently leverage the latest pre-exascale many-core and heterogeneous infrastructures are required. To this end we develop GR-Athena++, a new dynamical spacetime solver built on top of Athena++, that shows high-order convergence properties and excellent parallel scalability up to O(105) cores in full 3D binary black hole (BBH) merger simulations. Finally we present GR-AthenaK, the first performance-portable spacetime solver, obtained by refactoring GR-Athena++ with the Kokkos programming model. We demonstrate the correctness and convergence properties of GR-AthenaK with BBH runs on GPUs. GR-AthenaK shows a speedup ∼50 on one GPU compared to GR-Athena++ on a single CPU core.
Author: Francesco Zappa
Publisher:
ISBN:
Category :
Languages : de
Pages : 0
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Book Description
Numerical relativity (NR) simulations are crucial for studying the coalescence of compact binaries. Based on NR data, we produce a model for the mass and spin of the remnant black hole (BH) for the coalescence of black hole-neutron star systems, discussing its crucial role in gravitational wave (GW) modeling and in the parameter estimation of the two signals GW200105 and GW200115. In the context of binary neutron star merger simulations, we perform the first systematic study comparing results obtained with various neutrino treatments, the presence of turbulent viscosity and different grid resolutions. We find that the time of BH formation after merger is heavily affected by grid resolution and turbulent viscosity. An early BH formation limits matter ejection from the accretion disc, as the BH swallows a significant portion of it. Our results indicate that more reliable kilonova light curves are obtained only if the various ejecta components are present. Moreover, robust r-process nucleosynthesis yields require inclusion of both neutrino emission and reabsorption in simulations. Advanced neutrino schemes and turbulent viscosity in simulations resolved beyond current standards appear necessary for reliable astrophysical predictions. To carry out computationally demanding simulations of growing complexity, next-generation NR codes that can efficiently leverage the latest pre-exascale many-core and heterogeneous infrastructures are required. To this end we develop GR-Athena++, a new dynamical spacetime solver built on top of Athena++, that shows high-order convergence properties and excellent parallel scalability up to O(105) cores in full 3D binary black hole (BBH) merger simulations. Finally we present GR-AthenaK, the first performance-portable spacetime solver, obtained by refactoring GR-Athena++ with the Kokkos programming model. We demonstrate the correctness and convergence properties of GR-AthenaK with BBH runs on GPUs. GR-AthenaK shows a speedup ∼50 on one GPU compared to GR-Athena++ on a single CPU core.
Author: Koutarou Kyutoku
Publisher: Springer Science & Business Media
ISBN: 4431542019
Category : Science
Languages : en
Pages : 187
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Book Description
This thesis presents a systematic study of the orbital evolution, gravitational wave radiation, and merger remnant of the black hole–neutron star binary merger in full general relativity for the first time. Numerical-relativity simulations are performed using an adaptive mesh refinement code, SimulAtor for Compact objects in Relativistic Astrophysics (SACRA), which adopts a wide variety of zero-temperature equations of state for the neutron star matter. Gravitational waves provide us with quantitative information on the neutron star compactness and equation of state via the cutoff frequency in the spectra, if tidal disruption of the neutron star occurs before the binary merges. The cutoff frequency will be observed by next-generation laser interferometric ground-based gravitational wave detectors, such as Advanced LIGO, Advanced VIRGO, and KAGRA. The author has also determined that the mass of remnant disks are sufficient for the remnant black hole accretion disk to become a progenitor of short-hard gamma ray bursts accompanied by tidal disruptions and suggests that overspinning black holes may not be formed after the merger of even an extremely spinning black hole and an irrotational neutron star.
Author: Francesco Maria Fabbri
Publisher:
ISBN:
Category :
Languages : de
Pages : 0
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Book Description
The era of Gravitational Waves Astronomy was launched after the success of the first observation run of the LIGO Scientific Collaboration and the VIRGO Collaboration. The large laser interferometers incredible achievement prompted the need of extensive studies in the field of compact astrophysical objects, such as Black Holes and Neutron Stars. Today, seven years after this event, the field of study underwent a notable expansion, corroborated by the detection of a signal coming from a Binary Neutron Star merger, together with its electro-magnetic counterpart, and, more recently, by the first detections of signals coming from mixed compact binaries, i.e. Black Hole- Neutron Star binaries. In this thesis work we span our attention across different aspects of compact objects mergers, including the inclusion of new physics into the already performing numerical relativity code BAM and the study of specific systems of compact objects. We first explore the treatment of neutrinos in case of Binary Neutron Star mergers and a tool to identify and further analyze regions containing trapped neutrinos, in the hot remnant of such mergers. Neutrinos, play in fact a key role into the rapid processes that characterize the formation of elements in the dynamical ejecta expelled during these catastrophic events. In the following we explore a variety of configurations of mixed compact binary systems. After the development of the new ID code Elliptica, and the steps taken to verify its accuracy, we make use of its capability to evolve sets of physical system with various properties. Exploring the space of parameters we study different spin configurations and magnitudes of single objects and their effects on the merger dynamics.
Author: Remo Ruffini
Publisher: World Scientific
ISBN: 9814630004
Category : Science
Languages : en
Pages : 2807
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Book Description
The Marcel Grossmann Meetings seek to further the development of the foundations and applications of Einstein's general relativity by promoting theoretical understanding in the relevant fields of physics, mathematics, astronomy and astrophysics and to direct future technological, observational, and experimental efforts. The meetings discuss recent developments in classical and quantum aspects of gravity, and in cosmology and relativistic astrophysics, with major emphasis on mathematical foundations and physical predictions, having the main objective of gathering scientists from diverse backgrounds for deepening our understanding of spacetime structure and reviewing the current state of the art in the theory, observations and experiments pertinent to relativistic gravitation. The range of topics is broad, going from the more abstract classical theory, quantum gravity, branes and strings, to more concrete relativistic astrophysics observations and modeling.The three volumes of the proceedings of MG13 give a broad view of all aspects of gravitational physics and astrophysics, from mathematical issues to recent observations and experiments. The scientific program of the meeting included 33 morning plenary talks during 6 days, and 75 parallel sessions over 4 afternoons. Volume A contains plenary and review talks ranging from the mathematical foundations of classical and quantum gravitational theories including recent developments in string/brane theories, to precision tests of general relativity including progress towards the detection of gravitational waves, and from supernova cosmology to relativistic astrophysics including such topics as gamma ray bursts, black hole physics both in our galaxy and in active galactic nuclei in other galaxies, and neutron star and pulsar astrophysics. Volumes B and C include parallel sessions which touch on dark matter, neutrinos, X-ray sources, astrophysical black holes, neutron stars, binary systems, radiative transfer, accretion disks, quasors, gamma ray bursts, supernovas, alternative gravitational theories, perturbations of collapsed objects, analog models, black hole thermodynamics, numerical relativity, gravitational lensing, large scale structure, observational cosmology, early universe models and cosmic microwave background anisotropies, inhomogeneous cosmology, inflation, global structure, singularities, chaos, Einstein-Maxwell systems, wormholes, exact solutions of Einstein's equations, gravitational waves, gravitational wave detectors and data analysis, precision gravitational measurements, quantum gravity and loop quantum gravity, quantum cosmology, strings and branes, self-gravitating systems, gamma ray astronomy, and cosmic rays and the history of general relativity.
Author: Masaru Shibata
Publisher: World Scientific
ISBN: 9814699748
Category : Science
Languages : en
Pages : 844
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Book Description
This book is composed of two parts: First part describes basics in numerical relativity, that is, the formulations and methods for a solution of Einstein's equation and general relativistic matter field equations. This part will be helpful for beginners of numerical relativity who would like to understand the content of numerical relativity and its background. The second part focuses on the application of numerical relativity. A wide variety of scientific numerical results are introduced focusing in particular on the merger of binary neutron stars and black holes.
Author: Thomas W. Baumgarte
Publisher: Cambridge University Press
ISBN: 1139643177
Category : Science
Languages : en
Pages : 717
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Book Description
Aimed at students and researchers entering the field, this pedagogical introduction to numerical relativity will also interest scientists seeking a broad survey of its challenges and achievements. Assuming only a basic knowledge of classical general relativity, the book develops the mathematical formalism from first principles, and then highlights some of the pioneering simulations involving black holes and neutron stars, gravitational collapse and gravitational waves. The book contains 300 exercises to help readers master new material as it is presented. Numerous illustrations, many in color, assist in visualizing new geometric concepts and highlighting the results of computer simulations. Summary boxes encapsulate some of the most important results for quick reference. Applications covered include calculations of coalescing binary black holes and binary neutron stars, rotating stars, colliding star clusters, gravitational and magnetorotational collapse, critical phenomena, the generation of gravitational waves, and other topics of current physical and astrophysical significance.
Author: John L. Friedman
Publisher: Cambridge University Press
ISBN: 1107310601
Category : Science
Languages : en
Pages : 435
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Book Description
The masses of neutron stars are limited by an instability to gravitational collapse and an instability driven by gravitational waves limits their spin. Their oscillations are relevant to x-ray observations of accreting binaries and to gravitational wave observations of neutron stars formed during the coalescence of double neutron-star systems. This volume includes more than forty years of research to provide graduate students and researchers in astrophysics, gravitational physics and astronomy with the first self-contained treatment of the structure, stability and oscillations of rotating neutron stars. This monograph treats the equations of stellar equilibrium; key approximations, including slow rotation and perturbations of spherical and rotating stars; stability theory and its applications, from convective stability to the r-mode instability; and numerical methods for computing equilibrium configurations and the nonlinear evolution of their oscillations. The presentation of fundamental equations, results and applications is accessible to readers who do not need the detailed derivations.
Author: Luciano Rezzolla
Publisher: OUP Oxford
ISBN: 0191509914
Category : Science
Languages : en
Pages : 752
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Book Description
Relativistic hydrodynamics is a very successful theoretical framework to describe the dynamics of matter from scales as small as those of colliding elementary particles, up to the largest scales in the universe. This book provides an up-to-date, lively, and approachable introduction to the mathematical formalism, numerical techniques, and applications of relativistic hydrodynamics. The topic is typically covered either by very formal or by very phenomenological books, but is instead presented here in a form that will be appreciated both by students and researchers in the field. The topics covered in the book are the results of work carried out over the last 40 years, which can be found in rather technical research articles with dissimilar notations and styles. The book is not just a collection of scattered information, but a well-organized description of relativistic hydrodynamics, from the basic principles of statistical kinetic theory, down to the technical aspects of numerical methods devised for the solution of the equations, and over to the applications in modern physics and astrophysics. Numerous figures, diagrams, and a variety of exercises aid the material in the book. The most obvious applications of this work range from astrophysics (black holes, neutron stars, gamma-ray bursts, and active galaxies) to cosmology (early-universe hydrodynamics and phase transitions) and particle physics (heavy-ion collisions). It is often said that fluids are either seen as solutions of partial differential equations or as "wet". Fluids in this book are definitely wet, but the mathematical beauty of differential equations is not washed out.
Author: Miguel Alcubierre
Publisher: OUP Oxford
ISBN: 0191548294
Category : Science
Languages : en
Pages : 464
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Book Description
This book introduces the modern field of 3+1 numerical relativity. The book has been written in a way as to be as self-contained as possible, and only assumes a basic knowledge of special relativity. Starting from a brief introduction to general relativity, it discusses the different concepts and tools necessary for the fully consistent numerical simulation of relativistic astrophysical systems, with strong and dynamical gravitational fields. Among the topics discussed in detail are the following: the initial data problem, hyperbolic reductions of the field equations, gauge conditions, the evolution of black hole space-times, relativistic hydrodynamics, gravitational wave extraction and numerical methods. There is also a final chapter with examples of some simple numerical space-times. The book is aimed at both graduate students and researchers in physics and astrophysics, and at those interested in relativistic astrophysics.
Author: Gabriele Ghisellini
Publisher: Springer
ISBN: 3319006126
Category : Science
Languages : en
Pages : 152
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Book Description
This book grew out of the author’s notes from his course on Radiative Processes in High Energy Astrophysics. The course provides fundamental definitions of radiative processes and serves as a brief introduction to Bremsstrahlung and black body emission, relativistic beaming, synchrotron emission and absorption, Compton scattering, synchrotron self-compton emission, pair creation and emission. The final chapter discusses the observed features of Active Galactic Nuclei and their interpretation based on the radiative processes presented in the book. Written in an informal style, this book will guide students through their first encounter with high-energy astrophysics.
