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Symmetry
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Numerical Relativity and Gravitational Wave
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Numerical Relativity and Gravitational Wave

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Physics".

Deadline for manuscript submissions: closed (15 January 2023) | Viewed by 14046

Special Issue Editor

Prof. Dr. Sebastiano Bernuzzi

E-Mail Website
Guest Editor
Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universität Jena, 07743 Jena, Germany
Interests: general relativity; numerical relativity; gravitational wave

Special Issue Information

Dear Colleagues,

Numerical relativity (NR) is currently a major topic connecting general relativity to computational astrophysics and simulation science. After the 2006 breakthroughs in the simulation of black hole collisions, the field developed in several directions. Current applications range from multimessenger astrophysics modeling to cosmology, with new formal and numerical aspects under development.

Key astrophysical NR applications involve the simulations of mergers of neutron stars and black holes and of core collapse supernovae. Binary black hole simulations crucially helped the characterization of the first gravitational signals detected by the LIGO-Virgo experiments. Their increasing accuracy and completeness is driving waveform modeling for gravitationalwave astronomy. General relativistic fluidynamics simulations of compact binary mergers are essential to study the engines that power electromagnetic observables. Strong gravity is also a primary component for quantitative simulations of stellar collapse and accretion onto compact objects.

Fundamental applications of NR tools are the dynamical stability of compact objects, scenarios for black hole formation, and investigations of the cosmic censorship conjecture. Critical phenomena in gravitational collapse were a genuine numerical discovery and are currently being extended to nonspherical symmetries and multidimensions. High-energy black-hole collisions can be used to probe black-hole formation in proton–proton collisions at particle colliders or in cosmic-ray showers hitting the Earth’s atmosphere. The field is evolving also towards the exploration of alternative theories of gravity, black-hole studies in the context of the gauge–gravity duality, and the first cosmological applications.

The purpose of this Special Issue is to collect new original contributions in the broad field of numerical relativity. We welcome contributions exploring new formalisms and new numerical methods for Einstein equations, as well as new applications of NR methods in all areas.

Submit your paper and select the Journal “Symmetry” and the Special Issue “Numerical Relativity and Gravitational Wave” via: MDPI submission system. Our papers will be published on a rolling basis and we will be pleased to receive your submission once you have finished it.

Prof. Dr. Sebastiano Bernuzzi
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Mathematical and numerical advances in the initial data problem
  • Formulations for 3+1 NR and well-posedness
  • Relativistic hydrodynamics
  • Numerical methods for Einstein equations
  • High-performance computing for NR
  • Compact binaries and supernovae simulations
  • High-energy black-hole collisions
  • Gravitational waveform modeling with NR
  • Modeling multimessenger signals with NR
  • Critical collapse
  • NR cosmology
  • NR beyond general relativity.

Published Papers (5 papers)

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Research

26 pages, 3856 KiB  
Article
Deflection Angle and Shadow of the Reissner–Nordström Black Hole with Higher-Order Magnetic Correction in Einstein-Nonlinear-Maxwell Fields
by Yashmitha Kumaran and Ali Övgün
Symmetry 2022, 14(10), 2054; https://doi.org/10.3390/sym14102054 - 2 Oct 2022
Cited by 31 | Viewed by 2485
Abstract
Nonlinear electrodynamics is known as the generalizations of Maxwell electrodynamics at strong fields and presents interesting features such as curing the classical divergences present in the linear theory when coupled to general relativity. In this paper, we consider the asymptotically flat Reissner–Nordström black [...] Read more.
Nonlinear electrodynamics is known as the generalizations of Maxwell electrodynamics at strong fields and presents interesting features such as curing the classical divergences present in the linear theory when coupled to general relativity. In this paper, we consider the asymptotically flat Reissner–Nordström black hole solution with higher-order magnetic correction in Einstein-nonlinear-Maxwell fields. We study the effect of the magnetic charge parameters on the black hole, viz., weak deflection angle of photons and massive particles using the Gauss–Bonnet theorem. Moreover, we apply Keeton–Petters formalism to confirm our results concerning the weak deflection angle. Apart from a vacuum, their influence in the presence of different media such as plasma and dark matter are probed as well. Finally, we examine the black hole shadow cast using the null-geodesics method and investigate its spherically in-falling thin accretion disk. Our inferences show how the magnetic charge parameter p affects the other physical quantities; so, we impose some constraints on this parameter using observations from the Event Horizon Telescope. Full article
(This article belongs to the Special Issue Numerical Relativity and Gravitational Wave)
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17 pages, 2401 KiB  
Article
Machine Learning for Conservative-to-Primitive in Relativistic Hydrodynamics
by Tobias Dieselhorst, William Cook, Sebastiano Bernuzzi and David Radice
Symmetry 2021, 13(11), 2157; https://doi.org/10.3390/sym13112157 - 11 Nov 2021
Cited by 5 | Viewed by 2137
Abstract
The numerical solution of relativistic hydrodynamics equations in conservative form requires root-finding algorithms that invert the conservative-to-primitive variables map. These algorithms employ the equation of state of the fluid and can be computationally demanding for applications involving sophisticated microphysics models, such as those [...] Read more.
The numerical solution of relativistic hydrodynamics equations in conservative form requires root-finding algorithms that invert the conservative-to-primitive variables map. These algorithms employ the equation of state of the fluid and can be computationally demanding for applications involving sophisticated microphysics models, such as those required to calculate accurate gravitational wave signals in numerical relativity simulations of binary neutron stars. This work explores the use of machine learning methods to speed up the recovery of primitives in relativistic hydrodynamics. Artificial neural networks are trained to replace either the interpolations of a tabulated equation of state or directly the conservative-to-primitive map. The application of these neural networks to simple benchmark problems shows that both approaches improve over traditional root finders with tabular equation-of-state and multi-dimensional interpolations. In particular, the neural networks for the conservative-to-primitive map accelerate the variable recovery by more than an order of magnitude over standard methods while maintaining accuracy. Neural networks are thus an interesting option to improve the speed and robustness of relativistic hydrodynamics algorithms. Full article
(This article belongs to the Special Issue Numerical Relativity and Gravitational Wave)
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36 pages, 447 KiB  
Article
Multifluid Modelling of Relativistic Radiation Hydrodynamics
by Lorenzo Gavassino, Marco Antonelli and Brynmor Haskell
Symmetry 2020, 12(9), 1543; https://doi.org/10.3390/sym12091543 - 18 Sep 2020
Cited by 19 | Viewed by 1946
Abstract
The formulation of a universal theory for bulk viscosity and heat conduction represents a theoretical challenge for our understanding of relativistic fluid dynamics. Recently, it was shown that the multifluid variational approach championed by Carter and collaborators has the potential to be a [...] Read more.
The formulation of a universal theory for bulk viscosity and heat conduction represents a theoretical challenge for our understanding of relativistic fluid dynamics. Recently, it was shown that the multifluid variational approach championed by Carter and collaborators has the potential to be a general and natural framework to derive (hyperbolic) hydrodynamic equations for relativistic dissipative systems. Furthermore, it also allows keeping direct contact with non-equilibrium thermodynamics, providing a clear microscopic interpretation of the elements of the theory. To provide an example of its universal applicability, in this paper we derive the fundamental equations of the radiation hydrodynamics directly in the context of Carter’s multifluid theory. This operation unveils a novel set of thermodynamic constraints that must be respected by any microscopic model. Then, we prove that the radiation hydrodynamics becomes a multifluid model for bulk viscosity or heat conduction in some appropriate physical limits. Full article
(This article belongs to the Special Issue Numerical Relativity and Gravitational Wave)
21 pages, 4597 KiB  
Article
Structure of Neutron Stars in Massive Scalar-Tensor Gravity
by Roxana Rosca-Mead, Christopher J. Moore, Ulrich Sperhake, Michalis Agathos and Davide Gerosa
Symmetry 2020, 12(9), 1384; https://doi.org/10.3390/sym12091384 - 19 Aug 2020
Cited by 19 | Viewed by 2877
Abstract
We compute families of spherically symmetric neutron-star models in two-derivative scalar-tensor theories of gravity with a massive scalar field. The numerical approach we present allows us to compute the resulting spacetimes out to infinite radius using a relaxation algorithm on a compactified grid. [...] Read more.
We compute families of spherically symmetric neutron-star models in two-derivative scalar-tensor theories of gravity with a massive scalar field. The numerical approach we present allows us to compute the resulting spacetimes out to infinite radius using a relaxation algorithm on a compactified grid. We discuss the structure of the weakly and strongly scalarized branches of neutron-star models thus obtained and their dependence on the linear and quadratic coupling parameters α0, β0 between the scalar and tensor sectors of the theory, as well as the scalar mass μ. For highly negative values of β0, we encounter configurations resembling a “gravitational atom”, consisting of a highly compact baryon star surrounded by a scalar cloud. A stability analysis based on binding-energy calculations suggests that these configurations are unstable and we expect them to migrate to models with radially decreasing baryon density and scalar field strength. Full article
(This article belongs to the Special Issue Numerical Relativity and Gravitational Wave)
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18 pages, 2183 KiB  
Article
Binary Neutron Star Merger Simulations with a Calibrated Turbulence Model
by David Radice
Symmetry 2020, 12(8), 1249; https://doi.org/10.3390/sym12081249 - 29 Jul 2020
Cited by 49 | Viewed by 3441
Abstract
Magnetohydrodynamic (MHD) turbulence in neutron star (NS) merger remnants can impact their evolution and multi-messenger signatures, complicating the interpretation of present and future observations. Due to the high Reynolds numbers and the large computational costs of numerical relativity simulations, resolving all the relevant [...] Read more.
Magnetohydrodynamic (MHD) turbulence in neutron star (NS) merger remnants can impact their evolution and multi-messenger signatures, complicating the interpretation of present and future observations. Due to the high Reynolds numbers and the large computational costs of numerical relativity simulations, resolving all the relevant scales of the turbulence will be impossible for the foreseeable future. Here, we adopt a method to include subgrid-scale turbulence in moderate resolution simulations by extending the large-eddy simulation (LES) method to general relativity (GR). We calibrate our subgrid turbulence model with results from very-high-resolution GRMHD simulations, and we use it to perform NS merger simulations and study the impact of turbulence. We find that turbulence has a quantitative, but not qualitative, impact on the evolution of NS merger remnants, on their gravitational wave signatures, and on the outflows generated in binary NS mergers. Our approach provides a viable path to quantify uncertainties due to turbulence in NS mergers. Full article
(This article belongs to the Special Issue Numerical Relativity and Gravitational Wave)
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