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Compare Neutron Star Inspiral and Premature Collapse. Jian Tao ( jtao@wugrav.wustl.edu ) 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

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compare neutron star inspiral and premature collapse

Compare Neutron Star Inspiral and Premature Collapse

Jian Tao ( jtao@wugrav.wustl.edu )

Washington University Gravity Group

MWRM-16 Nov 18th, 2006

introduction
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
GR-Astro-AMR implementation
  • 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
  • Computer Science Side
    • High level programming abstraction with Cactus
    • Adaptive grid hierarchy implementation withGrACE
    • Interconnection between Cactus and GrACE with PAGH
neutron star inspiral i
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
Neutron star inspiral (II)

Zoomed into the central region

neutron star inspiral iii
Neutron star inspiral (III)
  • Geodesic separation
    • Different touching time means different phase of gravitational waves
inspiral analysis rest mass
Inspiral analysis (Rest Mass)
  • Rest mass
    • Baryon number shouldn’t be changed
    • Rest mass should stay the same
inspiral analysis rest mass1
Inspiral analysis (Rest Mass)
  • Rest Mass
    • HRSC scheme helps to conserve the rest mass
inspiral analysis constraints
Inspiral analysis (Constraints)
  • Constraints
    • Ham_Max and abs(Ham_Min) (left)
    • Convergence test for evolution (right)
compare conserved quantities
Compare conserved quantities
  • ADM Mass
    • Small computational boundaries contribute to the conservation of ADM mass by retaining gravitational waves

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)

compare conserved quantities1
Compare conserved quantities
  • Angular Momentum
    • Higher resolution better conservation
    • Oscillations might come from initial data

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)

premature collapse problem i
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
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
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 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