Simulations of Core-collapse Supernovae in Spatial Axisymmetry with Full Boltzmann Neutrino Transport

Abstract

We present the first results of our spatially axisymmetric core-collapse supernova simulations with full Boltzmann neutrino transport, which amount to a time-dependent 5-dimensional (2 in space and 3 in momentum space) problem in fact. Special relativistic effects are fully taken into account with a two-energy-grid technique. We performed two simulations for a progenitor of 11.2M ⊙ , employing different nuclear equations-of-state (EOS's): Lattimer and Swesty's EOS with the incompressibility of K = 220MeV (LS EOS) and Furusawa's EOS based on the relativistic mean field theory with the TM1 parameter set (FS EOS). In the LS EOS the shock wave reaches ∼ 700km at 300ms after bounce and is still expanding whereas in the FS EOS it stalled at ∼ 200km and has started to recede by the same time. This seems to be due to more vigorous turbulent motions in the former during the entire post-bounce phase, which leads to higher neutrino-heating efficiency in the neutrino-driven convection. We also look into the neutrino distributions in momentum space, which is the advantage of the Boltzmann transport over other approximate methods. We find non-axisymmetric angular distributions with respect to the local radial direction, which also generate off-diagonal components of the Eddington tensor. We find that the rθ-component reaches ∼ 10% of the dominant rr-component and, more importantly, it dictates the evolution of lateral neutrino fluxes, dominating over the θθ-component, in the semi-transparent region. These data will be useful to further test and possibly improve the prescriptions used in the approximate methods.

Fast-pairwise Collective Neutrino Oscillations Associated with Asymmetric Neutrino Emissions in Core-collapse Supernovae

“…The disparity in the number densities between ν e andν e is reduced by the anti-correlation of their number fluxes in the same hemisphere, and a preferable condition for the ELN crossing is produced. It should be also noted that asymmetric neutrino emissions were not observed in our previous CCSN model (Nagakura et al 2018), which would be the main reason why Delfan Azari et al (2019) found no ELN crossings in the post-shock region.…”

“…The details of the code development of our Boltzmann solver are described in a series of papers Nagakura et al 2014Nagakura et al , 2017Nagakura et al , 2019d and its reliability has been well established by a detailed comparison to another Monte-Carlo neutrino transport code (Richers et al 2017). Some results of axisymmetric CCSN simulations by using our code can be seen in Nagakura et al (2018); Harada et al (2019); Nagakura et al (2019c).…”

“…In this paper we tackle the former issue, focusing on fast flavor conversions (Sawyer 2005(Sawyer , 2016Chakraborty et al 2016b;Izaguirre et al 2017;Capozzi et al 2017;Dasgupta et al 2017;Dasgupta & Sen 2018;Dasgupta et al 2018;Airen et al 2018;Abbar & Volpe 2019a;Delfan Azari et al 2019). It should be noted that our CCSN simulations are capable of assessing occurrences of fast flavor conversion, since it feeds on the difference in the angular distributions among different species of neutrinos in momentum space, which is accessible only to the multi-angle neutrino transport like ours (Nagakura et al 2018;Harada et al 2019;Nagakura et al 2019c). The methodology in this study is essentially the same as that in Delfan Azari et al (2019).…”

Impact of Neutrino Opacities on Core-collapse Supernova Simulations

“…Non-linear turbulent flows associated with convective overturn and the standingaccretion-shock-instability (SASI, Blondin et al (2003)) increase the neutrino heating efficiency in the gain region, essentially aiding the explosion (see Janka (2017a); Müller (2016); Hix et al (2016); Foglizzo et al (2015); Burrows (2013); Kotake et al (2012) for reviews). In fact, a growing number of neutrino-driven models have been reported so far in self-consistent two-dimensional (2D) simulations, which has supported the validity of the multi-D neutrino-driven mechanism (e.g., Marek & Janka (2009) ;Suwa et al (2010); Müller et al (2012a); Dolence et al (2014); Nakamura et al (2015); Pan et al (2016); O'Connor & Couch (2015); Burrows et al (2016); Summa et al (2016); Nagakura et al (2017); Müller et al (2017)). …”

“…However, consideration of higher moments (Pons et al 1998), full set of velocity dependent terms (equivalently treatment of full energy-group couplings in the transport equations), and neutrino-flavor coupling is surely needed for more sophisticated simulations (e.g., Rampp & Janka (2002a) In our multi-D simulations, we apply a ray-by-ray approach where the neutrino transport is solved along a given radial direction assuming that the hydrodynamic medium for the direction is spherically symmetric. This also remains to be updated with more advanced schemes (e.g., Skinner et al (2016); Nagakura et al (2017)). …”