Current Affiliation Organization 【 display / non-display 】

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Research Theme 【 display / non-display 】

• Relativistic Astrophysics and Gravitational Wave Physics

Published Papers 【 display / non-display 】

Published Papers 【 display / non-display 】

• General-relativistic resistive-magnetohydrodynamics simulations of self-consistent magnetized rotating neutron stars

  Cheong P.C.K.

  Physical Review D ( Physical Review D )  111 ( 6 )   2025.03 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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    DOI

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

  Boukas Lambros, Tsokaros Antonios, Uryu Koji

  Universe ( MDPI )  10 ( 5 ) 1 - 25   2024.05 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  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 sets 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 of 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.

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    CiNii Research

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

  Boukas, L; Tsokaros, A; Uryu, K

  UNIVERSE ( Universe )  10 ( 5 )   2024.05 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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• General Relativistic Stability and Gravitational Wave Content of Rotating Triaxial Neutron Stars

  Luo, YF; Tsokaros, A; Haas, R; Uryu, K

  SYMMETRY-BASEL ( Symmetry )  16 ( 3 ) 1 - 13   2024.03 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  Triaxial neutron stars can be sources of continuous gravitational radiation detectable by ground-based interferometers. The amplitude of the emitted gravitational wave can be greatly affected by the state of the hydrodynamical fluid flow inside the neutron star. In this work, we examine the most triaxial models along two sequences of constant rest mass, confirming their dynamical stability. We also study the response of a triaxial figure of quasiequilibrium under a variety of perturbations that lead to different fluid flows. Starting from the general relativistic compressible analog of the Newtonian Jacobi ellipsoid, we perform simulations of Dedekind-type flows. We find that in some cases the triaxial neutron star resembles a Riemann-S-type ellipsoid with minor rotation and gravitational wave emission as it evolves towards axisymmetry. The present results highlight the importance of understanding the fluid flow in the interior of a neutron star in terms of its gravitational wave content.

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• Equilibriums of extremely magnetized compact stars with force-free magnetotunnels

  Koji Uryu, Shijun Yoshida, Eric Gourgoulhon, Charalampos Markakis, Kotaro Fujisawa, Antonios Tsokaros, Keisuke Taniguchi, Mina Zamani

  Physical Review D ( American Physical Society (APS) )  107 ( 10 ) 103016-1 - 103016-14   2023.05 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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Grant-in-Aid for Scientific Research 【 display / non-display 】

Grant-in-Aid for Scientific Research 【 display / non-display 】

• Initial data for numerical relativity simulations associated with standing waves

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2022.04  -   

  Investigator(s): Koji Uryu 

  Direct: 3,200,000 (YEN)  Overheads: 960,000 (YEN)  Total: 4,160,000 (YEN)

• Initial data for numerical relativity simulations associated with standing waves

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2022.04  -  2025.03 

  Direct: 3,200,000 (YEN)  Overheads: 4,160,000 (YEN)  Total: 960,000 (YEN)

• Initial data for numerical relativity simulations associated with standing waves

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2022.04  -  2025.03 

  Direct: 3,200,000 (YEN)  Overheads: 4,160,000 (YEN)  Total: 960,000 (YEN)

• Construction of various initial data for numerical relativity simulations

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2018.04  -   

  Investigator(s): Koji Uryu 

  Direct: 3,400,000 (YEN)  Overheads: 1,020,000 (YEN)  Total: 4,420,000 (YEN)

• Construction of various initial data for numerical relativity simulations

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2018.04  -  2023.03 

  Direct: 3,400,000 (YEN)  Overheads: 4,420,000 (YEN)  Total: 1,020,000 (YEN)

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