A new code for equilibriums and quasiequilibrium initial data of compact objects

Antonios Tsokaros; Koji Uryu

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A new code for equilibriums and quasiequilibrium initial data of compact objects

Koji Uryu, Antonios Tsokaros

General Relativity and Quantum Cosmology · Submitted 15 Aug 2011

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim We present a new code, named COCAL - Compact Object CALculator, for the computation of equilibriums and quasiequilibrium initial data sets of single or binary compact objects of all kinds.

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arXiv listing abstract v2. Results and the main claim are underlined; show every role.

We present a new code, named COCAL - Compact Object CALculator, for the computation of equilibriums and quasiequilibrium initial data sets of single or binary compact objects of all kinds. In the cocal code, those solutions are calculated on one or multiple spherical coordinate patches covering the initial hypersurface up to the asymptotic region. The numerical method used to solve field equations written in elliptic form is an adaptation of self-consistent field iterations in which Green's integral formula is computed using multipole expansions and standard finite difference schemes. We extended the method so that it can be used on a computational domain with excised regions for a black hole and a binary companion. Green's functions are constructed for various types of boundary conditions imposed at the surface of the excised regions for black holes. The numerical methods used in cocal are chosen to make the code simpler than any other recent initial data codes, accepting the second order accuracy for the finite difference schemes. We perform convergence tests for time symmetric single black hole data on a single coordinate patch, and binary black hole data on multiple patches. Then, we apply the code to obtain spatially conformally flat binary black hole initial data using boundary conditions including the one based on the existence of equilibrium apparent horizons.

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What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	We present a new code, named COCAL - Compact Object CALculator, for the computation of equilibriums and quasiequilibrium initial data sets of single or binary compact objects of all kinds.	contribution 1.00	0.94	0.40	asserted 1.00
s1	In the cocal code, those solutions are calculated on one or multiple spherical coordinate patches covering the initial hypersurface up to the asymptotic region.	method 0.99	0.77	0.04	asserted 1.00
s2	The numerical method used to solve field equations written in elliptic form is an adaptation of self-consistent field iterations in which Green's integral formula is computed using multipole expansions and standard finite difference schemes.	method 1.00	0.74	0.06	asserted 1.00
s3	We extended the method so that it can be used on a computational domain with excised regions for a black hole and a binary companion.	method 0.54	0.94	0.07	asserted 1.00
s4	Green's functions are constructed for various types of boundary conditions imposed at the surface of the excised regions for black holes.	method 0.90	0.91	0.04	asserted 1.00
s5	The numerical methods used in cocal are chosen to make the code simpler than any other recent initial data codes, accepting the second order accuracy for the finite difference schemes.	method 0.57	0.73	0.07	asserted 1.00
s6	We perform convergence tests for time symmetric single black hole data on a single coordinate patch, and binary black hole data on multiple patches.	method 0.87	0.96	0.05	asserted 1.00
s7	Then, we apply the code to obtain spatially conformally flat binary black hole initial data using boundary conditions including the one based on the existence of equilibrium apparent horizons.	result 0.59	0.96	0.20	asserted 1.00

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Original abstract

We present a new code, named COCAL - Compact Object CALculator, for the computation of equilibriums and quasiequilibrium initial data sets of single or binary compact objects of all kinds. In the cocal code, those solutions are calculated on one or multiple spherical coordinate patches covering the initial hypersurface up to the asymptotic region. The numerical method used to solve field equations written in elliptic form is an adaptation of self-consistent field iterations in which Green's integral formula is computed using multipole expansions and standard finite difference schemes. We extended the method so that it can be used on a computational domain with excised regions for a black hole and a binary companion. Green's functions are constructed for various types of boundary conditions imposed at the surface of the excised regions for black holes. The numerical methods used in cocal are chosen to make the code simpler than any other recent initial data codes, accepting the second order accuracy for the finite difference schemes. We perform convergence tests for time symmetric single black hole data on a single coordinate patch, and binary black hole data on multiple patches. Then, we apply the code to obtain spatially conformally flat binary black hole initial data using boundary conditions including the one based on the existence of equilibrium apparent horizons.

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Cited by 3 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

Kerr metric perturbations in Lorenz gauge via numerical relativity methods
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Direct Lorenz-gauge Kerr metric perturbations computed with an m-mode elliptic solver using discontinuous Galerkin methods, matching independent references to 1e-8 in redshift and 1e-10 in flux for spins up to |a|/M=0.998.
Self-force calculations with numerical relativity methods
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A new numerical relativity-inspired method achieves exponential convergence for scalar self-force calculations in Kerr spacetime on circular equatorial orbits up to near-extremal spins and the ISCO.
Binary neutron-star mergers: a review of Einstein's richest laboratory
gr-qc 2016-07 accept novelty 2.0 of 10

A comprehensive 2016 survey of binary neutron-star merger simulations, covering numerical methods, initial data, post-merger dynamics, magnetic fields, ejecta and nucleosynthesis, with the field's open questions catalogued.

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14 arXiv papers cite this in 22 sentences

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Papers citing it · 9 sentences without a confident label

Builds on it 1 paper

In this work, we present the extension of our Compact Object CALculator () code for BNSs [ref] to compute quasiequilibrium binary sequences of constant rest mass and circulation.

Constant circulation sequences of binary neutron stars and their spin characterization · Introduction · 0.86

Uses its method or tool 7 papers

First, we construct the most massive NSNSs in quasicircular orbit with the highest compactness to date using our initial data solver [ref] .

Great Impostors: Extremely Compact, Merging Binary Neutron Stars in the Mass Gap Posing as Binary Black Holes · Introduction · 1.00
For this purpose, we have prepared irrotational equal-mass BQS initial data with different total masses (3.0 $M_⊙$, 3.05 $M_⊙$ and 3.1 $M_⊙$ at infinite separation, and the models are referred to as MIT3.00, MIT3.05 and MIT3.10 through the texts) separated at an initial distance of 35 km with the code [ref] .

Evolution of equal mass binary bare quark stars in full general relativity: could a supramassive merger remnant experience prompt collapse? · The models · 1.00
To probe the effect of spin during the inspiral phase of a merging binary we evolve irrotational as well as spinning configurations that are constructed with our initial data solver [ref] in order to make a critical comparison.

Effect of spin on the inspiral of binary neutron stars · Initial data · 1.00

Cites it as background 2 papers

Many other codes exist for the construction of quasi-equilibrium NS binary systems, notably the spectral codes [ref] , [ref] , [ref] , [ref] , and the finite difference based code [ref] .

Quasi-equilibrium configurations of binary systems of dark matter admixed neutron stars · Introduction · 0.85
A wide range of approaches have been employed by different groups to set up ID for realistic astrophysical scenarios, including the use of finite difference [ref] , spectral [ref] , and Galerkin [ref] methods, which are then combined with special numerical techniques to solve the associated elliptic PDEs.

NRPyElliptic: A Fast Hyperbolic Relaxation Elliptic Solver for Numerical Relativity, I: Conformally Flat, Binary Puncture Initial Data · Introduction · 0.84

What it cites · 1 sentence without a confident label

Cites as background 4 papers

Several researchers have developed methods for computing various types of initial data sets for those simulations [ref] , and equilibriums of rotating compact objects (see e.g. [ref] ).

A new numerical method to construct binary neutron star initial data · Introduction · 0.97
In the last decades, simulation codes for compact objects have been successfully developed in the field of numerical relativity, and various dynamical simulations have been performed including binary neutron stars and black holes inspirals to merger [ref] , a massive core-collapse to a proto neutron star or a black hole (BH) formation [ref] , and black hole dynamics [ref] .

Formation of black hole and accretion disk in a massive high-entropy stellar core collapse · Introduction · 0.97
In the last decades, simulation codes for compact objects have been successfully developed in the field of numerical relativity, and various dynamical simulations have been performed including binary neutron stars and black holes inspirals to merger [ref] , a massive core-collapse to a proto neutron star or a black hole (BH) formation [ref] , and black hole dynamics [ref] .

Final State of Gregory-Laflamme Instability · Introduction · 0.97

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