51 research outputs found
A new baryonic equation of state at sub-nuclear densities for core-collapse simulations
We calculate a new equation of state for baryons at sub-nuclear densities
meant for the use in core-collapse simulations of massive stars. The abundance
of various nuclei is obtained together with the thermodynamic quantities. The
formulation is the NSE description and the liquid drop approximation of nuclei.
The model free energy to minimize is calculated by relativistic mean field
theory for nucleons and the mass formula for nuclei with the atomic number up
to ~ 1000. We have also taken into account the pasta phase, thanks to which the
transition to uniform nuclear matter in our EOS occurs in the conventional
manner: nuclei are not dissociated to nucleons but survive right up to the
transition to uniform nuclear matter. We find that the free energy and other
thermodynamical quantities are not very different from those given in the
Shen's EOS, one of the standard EOS's that adopt the single nucleus
approximation. The average mass is systematically different, on the other hand,
which may have an important ramification to the rates of electron captures and
coherent neutrino scatterings on nuclei in supernova cores. It is also
interesting that the root mean square of the mass number is not very different
from the average mass number, since the former is important for the evaluation
of coherent scattering rates on nuclei but has been unavailable so far. The EOS
table is currently under construction, which will include the weak interaction
rates.Comment: 34 pages, 11 figures, Accepted for publication Ap
On the Neutrino Distributions in Phase Space for the Rotating Core-collapse Supernova Simulated with a Boltzmann-neutrino-radiation-hydrodynamics Code
With the Boltzmann-radiation-hydrodynamics code, which we have developed to
solve numerically the Boltzmann equations for neutrino transfer, the Newtonian
hydrodynamics equations, and the Newtonian self-gravity simultaneously and
consistently, we simulate the collapse of a rotating core of the progenitor
with a zero-age-main-sequence mass of and a shelluler rotation
of at the center. We pay particular attention in this
paper to the neutrino distribution in phase space, which is affected by the
rotation. By solving the Boltzmann equations directly, we can assess the
rotation-induced distortion of the angular distribution in momentum space,
which gives rise to the rotational component of the neutrino flux. We compare
the Eddington tensors calculated both from the raw data and from the M1-closure
approximation. We demonstrate that the Eddington tensor is determined by
complicated interplays of the fluid velocity and the neutrino interactions and
that the M1-closure, which assumes that the Eddington factor is determined by
the flux factor, fails to fully capture this aspect, especially in the vicinity
of the shock. We find that the error in the Eddington factor reaches in our simulation. This is due not to the resolution but to the different
dependence of the Eddington and flux factors on the angular profile of the
neutrino distribution function, and hence modification to the closure relation
is needed.Comment: 24 pages, 23 figures, 0 explosion, published in Ap
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