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Compare Neutron Star Inspiral and Premature Collapse. Jian Tao ( [email protected] ) Washington University Gravity Group MWRM-16 Nov 18 th , 2006. Introduction. Our numerical implementations Neutron star inspiral simulations and some comparisons to other groups’ results - PowerPoint PPT Presentation
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Compare Neutron Star Inspiral and Premature Collapse
Jian Tao ( [email protected] )
Washington University Gravity Group
MWRM-16 Nov 18th, 2006
Introduction
Our numerical implementations Neutron star inspiral simulations and
some comparisons to other groups’ results
Premature collapse problem Conclusions and future plans
GR-Astro-AMR implementation
Computer Science Side High level programming abstraction with Cactus Adaptive grid hierarchy implementation with GrACE Interconnection between Cactus and GrACE with PAGH
Physics Side Initializing with unigrid code or by
interpolating
existing data sets Evolving with GR-Astro-AMR (HRSC code) Analyzing with AMR and unigrid analysis
code
Neutron star inspiral (I) Initial data (CFQE Spectral Data)
Binary Polytropic EOS EOS K=123.84 Gamma=2 Separation d : 39.5 km Omega : 2220.05 rad/s Baryon mass S1 : 1.625 M_sol Baryon mass S2 : 1.625 M_sol ADM mass : 2.995 M_sol Total ang mom: 8.53 M_sol^2
(K. Taniguchi, E. Gourgoulhon,Physical Review D 68, 124025, 2003)
Isolated Star Baryon mass : 1.625 M_sol ADM mass : 1.515 M_sol Proper radius : 11.99 M_sol
Neutron star inspiral (II)
Zoomed into the central region
Neutron star inspiral (III) Geodesic separation
Different touching time means different phase of gravitational waves
Inspiral analysis (Rest Mass) Rest mass
Baryon number shouldn’t be changed Rest mass should stay the same
Inspiral analysis (Rest Mass) Rest Mass
HRSC scheme helps to conserve the rest mass
Inspiral analysis (Constraints) Constraints
Ham_Max and abs(Ham_Min) (left) Convergence test for evolution (right)
Compare conserved quantities
dxyz = 0.46 M_s L=148 M_s(633,633,317) 240 GB memory
(Masaru Shibata, Keisuke Taniguchi & Koji Uryu, 2003)Less than 2.4GB memory
(GR-Astro-AMR results)
ADM Mass Small computational boundaries contribute to the
conservation of ADM mass by retaining gravitational waves
Compare conserved quantities
dxyz = 0.46 M_s L=148 M_s(633,633,317) 240 GB memory
(Masaru Shibata, Keisuke Taniguchi & Koji Uryu, 2003)
Less than 2.4GB memory(GR-Astro-AMR results)
Angular Momentum Higher resolution better conservation Oscillations might come from initial data
Premature Collapse Problem (I)
A Brief History J. Wilson and G. Mathews reported so called “neutron star
crushing effect” in 1995 Many papers published to disprove the crushing effect E. Flannagan pointed out an error in their formulation in
1999 J. Wilson and G. Mathews still found destabilization effect,
though small, in their simulations even after they fixed the error found by Flannagan
Mark Miller investigated the problem with fully dynamical general relativistic simulation in 2005
Premature Collapse Problem (II)
Theoretical analysis (E. Flannagan, 1998)
post-Newtonian matched asymptotic expansion works when R/r is small
Simulations carried out by Mark Miller start with corotational binary system
Question : what if R/r is big ? How about irrotational binaries ?
Decompression Effetc Numerical result
Proper radius of the isolated stars as R (same for both) Geodesic distance between two stars as the binary
separation
Summary and future works Summary
GR-Astro-AMR code is applied to study neutron star inspirals and compared to a similar uni-grid similation by other groups
Investigated premature collapse problem with full general relativistic simulations
Future plans Investigate other possible sources of errors Try and implement 4th order finite difference operators Look into non-CFQE initial data