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  • Multi-D Code Comparison - first steps

    Goals

    The goal is to create a simple yet complete set of conditions that can be easily simulated by many core-collapse groups. We want to strictly adhere to the same procedure for everything to minimize differences. Below we outline in detail the conditions for our tests, please comment if these are too strict, not strict enough, or if other conditions need to be considered.

    Discussion on Initial Conditions

    Oak Ridge cannot, as of yet, perform simulations with non-LS EOS. This presents a problem as this below set of initial conditions prevents their participation. The alternative, which is using the one of the LS EOS, is also undesirable because it opens up the can of worms that is low density EOS treatments, this was the reason for proposing the use the SFHo EOS, because it provides pressures (however inconsistent with reality) down to very low densities (1 g/ccm).

    Anyone have any suggestions? Does anyone want to do a LS220 simulation in addition to the SFHo simulation to provide a connect?

    Initial Conditions

    Non-neutrino Physics

    1. Progenitor: \(20\,M_\odot\) model from (WOOSLEY 2007). This model is available from the authors. Ideally, we would compare both a successful explosion and a failed explosion to test codes in both regimes. For this, we may need to add a second progenitor at a later stage. After seeing the outcome of these simulations.

    2. For mapping the progenitor, we will use density, temperature, and ye. Careful to note the definition of the radial coordinate in the initial model (radial coordinate is the location of the outer edge of the zone, the velocity is also defined at this radius, the remaining required quantities (rho, temperature, ye) are defined as cell averages).

    3. Equation of state: The SFHo nuclear equation of state from (Steiner 2013) available from http://phys-merger.physik.unibas.ch/~hempel/eos.html or http://www.stellarcollapse.org/equationofstate. This EOS extends down to densities of \(1\,\mathrm{g}\,\mathrm{cm}^{-3}\). In this EOS, NSE is assumed down to these densities (which is incorrect for supernovae). However, to eliminate (for now) issues related to low density equations of state and nuclear reaction networks, this study will use only the SFHo equation of state for all densities, temperatures, and ye’s.

    4. Boundary and Boundary Conditions: The SFHo EOS only goes down to \(0.1\,\)MeV, therefore the outer boundary must be closer than \(1.2\times 10^9\,\mathrm{cm}\). For this comparison, we would like the outer boundary to be taken as \(10^9\,\mathrm{cm}\). For the outer boundary conditions, fix the density and velocity so as to maintain a constant mass accretion rate. This is not the most physical boundary condition, but ensures the same condition is used by different groups.

    5. For multidimensional simulations, do collapse in 1D up to 15ms after bounce, then transition to 2D. Add perturbations via a clearly defined manner.

    6. Perform simulations using both Newtonian gravity and/or some form of general relativistic gravity (either effective potential, true GR).

    Neutrino Physics

    1. Use three species, \(\nu_e\), \(\bar{\nu}_e\), and \(\nu_x = \{\nu_\mu\) \(\bar{\nu}_\mu\), \(\nu_\tau\), and \(\bar{\nu}_\tau\}\).

    2. Use a clearly defined energy bin structure.

    3. The SFHo EOS contains light clusters. For this study, all neutrino interactions (both absorption and scattering) on light clusters is ignored.

    4. For scattering on free nucleons, use the (Bruenn 1985) rates. Include weak magnetism and recoil corrections via (Horowitz 2002).

    5. For scattering on heavy nuclei, use the (Bruenn 1985) rate, include ion-ion correlations via (Horowitz 1997), and a correction for the nuclear form factor via (Bruenn 1997, Rampp 2002).

    6. Include inelastic neutrino-electron scattering only in 1D simulations. This will include inelastic scattering during the collapse phase of 2D simulations as up to 15ms postbounce will be done in 1D.

    7. For pair processes, include electron-positron annihilation to neutrino pairs and nucleon-nucleon Bremsstrahlung. However, ignore neutrino pair conversion to other neutrino pairs.

    8. Use (Bruenn 1985) rates for absorption rates (on nucleons and nuclei). Include weak magnetism and recoil corrections for nucleon rates. Do not include any nucleon potentials, but still maintain the neutron-proton rest mass difference.

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