

CoCoNuT Meeting 2015
Nov. 1820, Malaga



Introduction:
CoCoNuT is a general relativistic hydrodynamics code with
dynamical spacetime evolution. The main aim of this
numerical code is the study of several astrophysical
scenarios in which general relativity can play an important
role, namely the collapse of rapidly rotating stellar cores
and the evolution of isolated neutron stars.
The code has two flavors: CoCoA, the axisymmetric (2D)
magnetized version, and CoCoNuT, the 3D nonmagnetized
version. The CoCoA project was started by Harald Dimmelmeier
at the
MaxPlanck Institute for Astrophysics
(Garching bei München, Germany) as part of his PhD
thesis. It was extended to 3D (CoCoNuT) in collaboration with
Jérôme Novak from the
LUTH
laboratory at the
Observatoire de Paris
(Meudon, France). This web page is intended to be a
presentation of the numerical code and its scientific
results. This code is not of public domain.
Features:
 3+1 in Spherical polar coordinates:
CoCoNuT uses the 3+1 decomposition of the Einstein
equations in spherical polar coordinates. This
coordinate system is very well adapted to the core collapse
scenario and neutron star evolution for which the code
is intended. It allows to reduce easily the
dimensionality of the problem in axisymmetry (2D) and in
spherical symmetry (1D).
 Godunovtype schemes:
The use of conservative methods (approximate Riemann solvers)
allows high accuracy in the
preservation of global quantities as mass or momentum and the
correct treatment of discontinuities during the evolution.
 CFC metric evolution:
For the metric evolution the conformally flatness condition (CFC)
approximation is used. This approximation has proven to be
very powerful in the core collapse scenario with extraordinary
good agreement with full general relativistic simulations.
 Mariage des Maillages:
The system of CFC equations consist in a set of elliptic nonlinear
equations which are solved with spectral methods by means of the
LORENE
library developed at
Meudon.
The interface between the spectral
grid for the metric and the finite differences grid
for the hydrodynamics is performed by means of the
"Mariage des Maillages" (grid wedding) technique.
 Microphysics:
Several equations of state can be used during the evolution,
from simple analytical expressions (polytropic, ideal gas, hybrid eos)
to microphysical equations of state in tabulated form (SHEN, LSEOS).
A parametrized deleptonization scheme allows a simplified neutrino
treatment during the collapse.
 GRMHD:
The axisymmetric version of the code (CoCoA) is able to solve
the ideal magnetohydrodynamics equations in general relativity.
The code uses constrained transport scheme to preserve the
solenoidal condition for the magnetic field. Furthermore it
has the ability of recovering the primitives variables
from the conserved ones with a robust procedure even in the case
of microphysical equations of state.
Authors:
The main contributors and maintainers to the CoCoNuT/CoCoA code are:
 Harald Dimmelmeier
 Jérôme Novak
 Pablo CerdáDurán
People currently working with and contributing to the code are:
 Isabel CorderoCarrión
 Ernazar B. Abdikamalov
The name:
CoCoNuT 
= Core Collapse with "Nu" (=new) Technology 
CoCoA 
= Core Collapse in Axisymmetry 
Comments to: Pablo CerdáDurán at uv.es
Last modified: Tue Jun 24 09:28:18 CEST 2008

