Strategies for the characteristic extraction of gravitational waveforms

Babiuc, Maria; Bishop, Nigel T.; Szilágyi, Béla; Winicour, Jeffrey

doi:10.1103/physrevd.79.084011

Cited by 48 publications

(114 citation statements)

References 45 publications

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“…The scheme is therefore not well suited for the evolution of the actual GW source. Characteristic evolutions, on the other hand, are well adapted to the far-field region of spacetime and can efficiently evolve the metric fields out to J + where it is possible to obtain Ψ 4 (and, hence, h) in a mathematically unambiguous and gauge-invariant way [46,[97][98][99].…”

Section: Cauchy-characteristic Extractionmentioning

confidence: 99%

Gravitational wave extraction in simulations of rotating stellar core collapse

et al. 2011

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We perform simulations of general relativistic rotating stellar core collapse and compute the gravitational waves (GWs) emitted in the core bounce phase of three representative models via multiple techniques. The simplest technique, the quadrupole formula (QF), estimates the GW content in the spacetime from the mass quadrupole tensor only. It is strictly valid only in the weakfield and slow-motion approximation. For the first time, we apply GW extraction methods in core collapse that are fully curvature-based and valid for strongly radiating and highly relativistic sources. These techniques are not restricted to weak-field and slow-motion assumptions. We employ three extraction methods computing (i) the Newman-Penrose (NP) scalar Ψ4, (ii) Regge-Wheeler-ZerilliMoncrief (RWZM) master functions, and (iii) Cauchy-Characteristic Extraction (CCE) allowing for the extraction of GWs at future null infinity, where the spacetime is asymptotically flat and the GW content is unambiguously defined. The latter technique is the only one not suffering from residual gauge and finite-radius effects. All curvature-based methods suffer from strong non-linear drifts. We employ the fixed-frequency integration technique as a high-pass waveform filter. Using the CCE results as a benchmark, we find that finite-radius NP extraction yields results that agree nearly perfectly in phase, but differ in amplitude by ∼ 1 − 7% at core bounce, depending on the model. RWZM waveforms, while in general agreeing in phase, contain spurious high-frequency noise of comparable amplitudes to those of the relatively weak GWs emitted in core collapse. We also find remarkably good agreement of the waveforms obtained from the QF with those obtained from CCE. The results from QF agree very well in phase and systematically underpredict peak amplitudes by ∼ 5−11%, which is comparable to the NP results and is certainly within the uncertainties associated with core collapse physics.

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Section: Cauchy-characteristic Extractionmentioning

confidence: 99%

Gravitational wave extraction in simulations of rotating stellar core collapse

et al. 2011

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“…As detailed in Refs. [27,62], it is necessary to apply a transformation from the induced gauge, denoted by coordinates (u, r, y A ), to Bondi gauge, denoted by coordinates (u B , r B , y A B ). The code presented in Refs.…”

Section: Wave Extraction In Bondi Gaugementioning

confidence: 99%

“…The code presented in Refs. [27,62] applies the relevant transformation to spatial Bondi gauge (r B , y A B ) and computes the Bondi time u B (u, y A B ) as a function of coordinate time u and angular coordinates y A B . In a final step, it is necessary to make the transformation u → u B to constant Bondi time u B (y A B ) = const.…”

Section: Wave Extraction In Bondi Gaugementioning

confidence: 99%

“…[27] computes the gravitational news function N , which in Bondi gauge is related to the metric component J by N = J ,ur . An alternative and independent method computes the Weyl scalar Ψ 4 [62], which is related to the news function by Ψ 4 = N ,u . Note that this last relation is not used in the characteristic code; the two quantities Ψ 4 and N are computed independently.…”

Section: Wave Extraction In Bondi Gaugementioning

confidence: 99%

“…Each patch contains N ang points per angular direction. The two angular patches use circular boundaries to eliminate noise from patch corners [62].…”

Section: Characteristic Evolutionsmentioning

confidence: 99%

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Comparing gravitational waveform extrapolation to Cauchy-characteristic extraction in binary black hole simulations

et al. 2013

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We extract gravitational waveforms from numerical simulations of black hole binaries computed using the Spectral Einstein Code. We compare two extraction methods: direct construction of the Newman-Penrose (NP) scalar Ψ4 at a finite distance from the source and Cauchy-characteristic extraction (CCE). The direct NP approach is simpler than CCE, but NP waveforms can be contaminated by near-zone effects-unless the waves are extracted at several distances from the source and extrapolated to infinity. Even then, the resulting waveforms can in principle be contaminated by gauge effects. In contrast, CCE directly provides, by construction, gauge-invariant waveforms at future null infinity. We verify the gauge invariance of CCE by running the same physical simulation using two different gauge conditions. We find that these two gauge conditions produce the same CCE waveforms but show differences in extrapolated-Ψ4 waveforms. We examine data from several different binary configurations and measure the dominant sources of error in the extrapolated-Ψ4 and CCE waveforms. In some cases, we find that NP waveforms extrapolated to infinity agree with the corresponding CCE waveforms to within the estimated error bars. However, we find that in other cases extrapolated and CCE waveforms disagree, most notably for m = 0 "memory" modes.

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Gravitational Wave Astrophysics

Sopuerta¹

2015

Astrophysics and Space Science Proceedings

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Strategies for the characteristic extraction of gravitational waveforms

Cited by 48 publications

References 45 publications

Gravitational wave extraction in simulations of rotating stellar core collapse

Gravitational wave extraction in simulations of rotating stellar core collapse

Comparing gravitational waveform extrapolation to Cauchy-characteristic extraction in binary black hole simulations

Gravitational Wave Astrophysics

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