Many of the earliest simulations of core-collapse supernovae used or were concerned with a general relativistic (GR) approach (Misner & Sharp 1964; Colgate & White 1966; May & White 1966; Wilson 1971; Bruenn 1985; Burrows 1988), and rightly so since neutron stars are sufficiently compact that GR dramatically effects their equilibrium structure. While the importance of including GR gravity in simulations of core-collapse supernovae has always persisted in the literature and is in use in many current and state-of-the-art multidimensional, core-collapse supernova calculations (Marek & Janka 2009; Kuroda et al. 2012; Müller et al. 2012a; Bruenn et al. 2013, 2016; Ott et al. 2013; Lentz et al. 2015; Skinner et al. 2016; Burrows et al. 2018), many modern simulations have used a purely Newtonian approximation for gravity (Takiwaki et al. 2014; Couch & O’Connor 2014; Handy et al. 2014; Couch & Ott 2015; Dolence et al. 2015; Nakamura et al. 2015; Pan et al. 2016; Suwa et al. 2016). Liebendörfer et al. (2001) extensively compared GR gravity and Newtonian gravity in spherical symmetry with a full Boltzmann neutrino transport solver. While their baseline simulations in both prescriptions of gravity fail to explode in 1D, their conclusion is that, overall, GR is helpful for the development of the core-collapse supernova explosion. This conclusion comes out of serendipitous simulations where incorrect nucleon isoenergetic scattering cross sections were used. In these simulations, when GR gravity was used, the simulation predicted an explosion, but when Newtonian gravity was used, the simulations failed to achieve explosions. Bruenn et al. (2001), Buras et al. (2006b), and Lentz et al. (2012) also compared Newtonian and GR simulations in spherical symmetry with energy-dependent neutrino transport. Like Liebendörfer et al. (2001), they observe higher neutrino luminosities and energies but do not extensively study the differences, in part because both simulations still fail to explode owing to the 1D nature of the simulations. Kuroda et al. (2012) examined the difference between special relativistic hydrodynamics and GR hydrodynamics in both 1D and 3D core-collapse simulations using approximate neutrino transport (a gray M1 scheme). However, while the 3D GR simulations show signs of increased susceptibility to explosion, the simulated time was not long enough to observe an explosion. Müller et al. (2012a) also investigated the influence of Newtonian gravity, GR gravity, and GR effective potential gravity in 2D core-collapse simulations using a variable-Eddington-factor, two-moment, energy-dependent neutrino transport scheme and the ray-by-ray+ approximation (where the neutrino transport is done along radial rays assuming spherical symmetry and with minimal coupling between neighboring rays). For the classic 15 M⊙ model from Woosley & Weaver (1995), Müller et al. (2012a) find a late and asymmetric explosion when using fully GR gravity, but not with Newtonian gravity, GR effective potential gravity, or reduced set neutrino opacities. This was, and still is, the most direct evidence that GR aids in the explosion mechanism. It is important to validate the hypothesis that GR gravity does indeed lead to more favorable conditions for explosion in modern-day simulations, with updated progenitor models, and loosening the assumption of spherically symmetric.
Citation: Nakamura et al. 2015
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