# Projects
### PROMETHEUS/VERTEX
PROMETHEUS/VERTEX is a multidimensional neutrino radiation
hydrodynamics code which was developed at MPA to simulate
supernova explosions of massive stars.
For the supernova problem an accurate computation of the
energy and lepton number source terms due to neutrino heating
is essential. Hence, the Boltzmann equation of neutrino transport
needs to be solved together with the hydrodynamics. Since
the transport problem requires:
- the solution of a highly dimensional problem in neutrino
phase space per time step
- implicit discretization to allow for sufficiently large
time steps a computational performance beyond a TFLOP/s
is necessary for this type of simulation.
#### Numerics
On a radial ray, angular moment equations of the Boltzmann
equation are discretized with backward time differencing,
giving rise to a non-linear algebraic system which is solved
with a Newton-Raphson procedure. Within a Newton-Raphson step,
inversions of a block-pentadiagonal matrix with dense blocks
are required. A similar Newton-Raphson procedure is employed
for solving a model Boltzmann equation. Both solutions are
iterated to consistency on each ray.
The entire code has been vectorized. Parallelization is performed
at a coarse level over the different radial rays. A mixed
OpenMP/MPI programming model has been used to assign radial
rays to different CPUs.
#### Simulation Results
The figure shows the snapshot from a simulation of the evolution
of the neutrino heated supernova shock in a 11.2 solar mass
star. The simulation was performd using a full 180 degree
computational grid.
A weak explosion with a prolate shock developed.
This low-resolution simulation required about half a year
of computation on a 32 CPU IBM p690.
So far, the supernova problem is still unsolved. The enormous
computational requirements have defied parameter studies for
identifying the crucial piece of physics in a successful supernova
simulation. Substantial progress in the field is expected
from TFlop simulations, which will allow to treat the neutrino
transport more accurately, and to vary uncertain input physics
in the simulations.
#### Contact
Konstantinos Kifonidis
Max-Planck-Institut für Astrophysik
Phone: ++49-89-30000-2245
Fax: ++49-89-30000-2235
E-Mail: kok@mpa-garching.mpg.de
Hans-Thomas Janka
Max-Planck-Institut für Astrophysik
Phone: ++49-89-30000-2228
Fax: ++49-89-30000-2235
E-Mail: thj@mpa-garching.mpg.de |