Smooth equations of state for high-accuracy simulations of neutron star binaries

High-accuracy numerical simulations of merging neutron stars play an important role in testing and calibrating the waveform models used by gravitational wave observatories. Obtaining high-accuracy waveforms at a reasonable computational cost, however, remains a significant challenge. One issue is th...

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Bibliographic Details
Published in:Physical review. D 2019-11, Vol.100 (10), p.1, Article 104048
Main Authors: Foucart, F., Duez, M., Gudinas, A., Hébert, F., Kidder, L., Pfeiffer, H., Scheel, M.
Format: Article
Language:English
Subjects:
Accuracy
Binary stars
Computational efficiency
Computer simulation
Equations of state
Gravitational waves
Mathematical models
Neutron stars
Neutrons
Observatories
Spectra
Star mergers
Waveforms
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Summary:High-accuracy numerical simulations of merging neutron stars play an important role in testing and calibrating the waveform models used by gravitational wave observatories. Obtaining high-accuracy waveforms at a reasonable computational cost, however, remains a significant challenge. One issue is that high-order convergence of the solution requires the use of smooth evolution variables, while many of the equations of state used to model the neutron star matter have discontinuities, typically in the first derivative of the pressure. Spectral formulations of the equation of state have been proposed as a potential solution to this problem. Here, we report on the numerical implementation of spectral equations of state in the spectral Einstein code. We show that, in our code, spectral equations of state allow for high-accuracy simulations at a lower computational cost than commonly used "piecewise polytrope" equations state. We also demonstrate that not all spectral equations of state are equally useful: different choices for the low-density part of the equation of state can significantly impact the cost and accuracy of simulations. As a result, simulations of neutron star mergers present us with a trade-off between the cost of simulations and the physical realism of the chosen equation of state.
ISSN:2470-0010
2470-0029
DOI:10.1103/PhysRevD.100.104048