199 research outputs found
Compact Binary Waveform Center-of-Mass Corrections
We present a detailed study of the center-of-mass (c.m.) motion seen in
simulations produced by the Simulating eXtreme Spacetimes (SXS) collaboration.
We investigate potential physical sources for the large c.m. motion in binary
black hole simulations and find that a significant fraction of the c.m. motion
cannot be explained physically, thus concluding that it is largely a gauge
effect. These large c.m. displacements cause mode mixing in the gravitational
waveform, most easily recognized as amplitude oscillations caused by the
dominant (2,2) modes mixing into subdominant modes. This mixing does not
diminish with increasing distance from the source; it is present even in
asymptotic waveforms, regardless of the method of data extraction. We describe
the current c.m.-correction method used by the SXS collaboration, which is
based on counteracting the motion of the c.m. as measured by the trajectories
of the apparent horizons in the simulations, and investigate potential methods
to improve that correction to the waveform. We also present a complementary
method for computing an optimal c.m. correction or evaluating any other c.m.
transformation based solely on the asymptotic waveform data.Comment: 20 pages, 15 figure
The SXS Collaboration catalog of binary black hole simulations
Accurate models of gravitational waves from merging black holes are necessary
for detectors to observe as many events as possible while extracting the
maximum science. Near the time of merger, the gravitational waves from merging
black holes can be computed only using numerical relativity. In this paper, we
present a major update of the Simulating eXtreme Spacetimes (SXS) Collaboration
catalog of numerical simulations for merging black holes. The catalog contains
2018 distinct configurations (a factor of 11 increase compared to the 2013 SXS
catalog), including 1426 spin-precessing configurations, with mass ratios
between 1 and 10, and spin magnitudes up to 0.998. The median length of a
waveform in the catalog is 39 cycles of the dominant
gravitational-wave mode, with the shortest waveform containing 7.0 cycles and
the longest 351.3 cycles. We discuss improvements such as correcting for moving
centers of mass and extended coverage of the parameter space. We also present a
thorough analysis of numerical errors, finding typical truncation errors
corresponding to a waveform mismatch of . The simulations provide
remnant masses and spins with uncertainties of 0.03% and 0.1% (
percentile), about an order of magnitude better than analytical models for
remnant properties. The full catalog is publicly available at
https://www.black-holes.org/waveforms .Comment: 33+18 pages, 13 figures, 4 tables, 2,018 binaries. Catalog metadata
in ancillary JSON file. v2: Matches version accepted by CQG. Catalog
available at https://www.black-holes.org/waveform
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Microfoundations
This paper argues that the microfoundations programme can be understood as an implementation of an underlying methodological principle—methodological individualism—and that it therefore shares a fundamental ambiguity with that principle, viz, whether the macro must be derived from and therefore reducible to, or rather consistent with, micro-level behaviours. The pluralist conclusion of the paper is not that research guided by the principle of microfoundations is necessarily wrong, but that the exclusion of approaches not guided by that principle is indeed necessarily wrong. The argument is made via an examination of the advantages claimed for dynamic stochastic general equilibrium models, the relationship between parts and wholes in social science, and the concepts of reduction, substrate neutrality, the intentional stance, and hypostatisation
Recommended from our members
Microfoundations
The paper argues that the microfoundations programme can be understood as an implementation of an underlying methodological principle, methodological individualism, and that it therefore shares a fundamental ambiguity with that principle, viz, whether the macro must be derived from and therefore reducible to, or rather consistent with micro-level behaviours. The pluralist conclusion of the paper is not that research guided by the principle of microfoundations is necessarily wrong, but that the exclusion of approaches not guided by that principle is indeed necessarily wrong. The argument is made via an examination of the advantages claimed for dynamic stochastic general equilibrium models, the relationship between parts and wholes in social science, and the concepts of reduction, substrate neutrality, the intentional stance, and hypostatisation
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