1,721,114 research outputs found
Constraint violation in free evolution schemes: Comparing the BSSNOK formulation with a conformal decomposition of the Z4 formulation
Full text linkGravitational waves from pulsations of neutron stars described by realistic equations of state
Full text linkIn this work we discuss the time evolution of nonspherical perturbations of a nonrotating neutron star described by a realistic equation of state (EOS). We analyze 10 different EOS for a large sample of neutron star models. Various kinds of generic initial data are evolved and the gravitational signals are computed. We focus on the dynamical excitation of fluid and spacetime modes and extract the corresponding frequencies. We employ a constrained numerical algorithm based on standard finite-differencing schemes which permits stable and long-term evolutions. Our code provides accurate waveforms and allows one to capture, via Fourier analysis, the frequencies of the fluid modes with an accuracy comparable to that of frequency-domain calculations. The results we present here are useful for providing comparisons with simulations of nonlinear oscillations of (rotating) neutron star models as well as test beds for 3D nonlinear codes. © 2008 The American Physical Society
Simulations of rotating neutron star collapse with the puncture gauge: End state and gravitational waveforms
Full text linkWe reexamine the gravitational collapse of rotating neutron stars to black holes by new 3+1 numerical relativity simulations employing the Z4c formulation of Einstein equations, the moving puncture gauge conditions, and a conservative mesh refinement scheme for the general relativistic hydrodynamics. The end state of the collapse is compared to the vacuum spacetime resulting from the evolution of spinning puncture initial data. Using a local analysis for the metric fields, we demonstrate that the two spacetimes actually agree. Gravitational waveforms are analyzed in some detail. We connect the emission of radiation to the collapse dynamics using simplified spacetime diagrams, and discuss the similarity of the waveform structure with the one of black hole perturbation theory
Numerical solution of the 2 + 1 Teukolsky equation on a hyperboloidal and horizon penetrating foliation of Kerr and application to late-time decays
Full text linkHorizon-absorption effects in coalescing black-hole binaries: An effective-one-body study of the nonspinning case
Full text linkModeling the Complete Gravitational Wave Spectrum of Neutron Star Mergers
Full text linkIn the context of neutron star mergers, we study the gravitational wave spectrum of the merger remnant using numerical relativity simulations. Postmerger spectra are characterized by a main peak frequency f_2 related to the particular structure and dynamics of the remnant hot hypermassive neutron star. We show that f_2 is correlated with the tidal coupling constant κ^T_2 that characterizes the binary tidal interactions during the late-inspiral merger. The relation f_2 (κ^T_2) depends very weakly on the binary total mass, mass ratio, equation of state, and thermal effects. This observation opens up the possibility of developing a model of the gravitational spectrum of every merger unifying the late-inspiral and postmerger descriptions
Accuracy of numerical relativity waveforms from binary neutron star mergers and their comparison with post-Newtonian waveforms
Full text linkImproved effective-one-body description of coalescing nonspinning black-hole binaries and its numerical-relativity completion
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