CITA Research September 2002 - August 2003
Computational Astrophysics
CITA's expertise and computing infrastructure continue to drive a
strong analysis and simulation effort. Current developments include
large scale parallel N-body, hydrodynamics, and magnetohydrodynamics.
CITA has hired a permanent parallel programmer to assist the
utilization of its high performance computing infrastructute. Current
hardware includes a 536 2.4 GHz CPU / 284 GB intel cluster, a
32-processor 64 GB shared memory Compaq alphaserver GS320, 8 quad es40
alphaservers, and intel and alpha linux clusters comprising upward of
100 processors.
Recent highlights include detailed simulations of the intergalactic
medium to model the Sunyaev-Zeldovich effect (Pen and Zhang;
Bond, Wadsley and Ruetalo); construction of a dedicated
out-of-core machine for cosmological gas and clustering simulations
(Pen and Trac); hydrodynamical simulations of cluster formation
(Loken and collaborators); hydrodynamical simulations of galaxy
interactions (Dubinski and collaborators); simulations of
two-phase protoplanetary disks (Humble and collaborators);
a new numerical method to solve the equations of MHD (Pen
and Arras); and precision calculations of the
internal modes of rotating stars (Arras, Pen, and Wu).
General relativistic supernova code
M. Liebendoerfer has completed the world's first detailed documentation of
a general relativistic supernova code with Boltzmann neutrino transport.
Accurate neutrino transport is essential to quantify the energy
deposition of outstreaming neutrinos behind the stalled shock. It
is still not known how the shock is revived to produce a supernova
explosion. M. Liebendoerfer has parallelized parts of the code with OMP
and adapted it to the SMP machines at CITA. New tools for the detailed
analysis of the calculated neutrino signal have been developed.
Comparison of numerical methods
M. Liebendoerfer, M. Rampp (Max-Planck Institute for Astrophysics,
Garching, MPA), H.-T. Janka (MPA), and A. Mezzacappa (Oak Ridge National
Laboratory, ORNL) have compared in detail their supernova simulations
implementing an implicit solution of the Boltzmann transport equation
or a variable Eddington factor method for the neutrino transport and
found satisfactory agreement in spherical symmetry.
Singularity excision algorithm
With D. Richmond (Univ. of Victoria), M. Liebendoerfer has
supplemented the adaptive grid in the hydrodynamics code AGILE with a
singularity excision algorithm to be combined with neutrino transport
in future predictions of the neutrino signal after a failed supernova
explosion.
Parallel code development
M. Liebendoerfer has created a new and concise implementation of cubic
domain decomposition with MPI for distributed memory computations in
the three-dimensional MHD code developed by Ue-Li Pen, Phil Arras, and
ShingKwong Wong. A concise and fast code facilitates student projects and
the extension with input physics. The Lattimer-Swesty equation of state
has been tabulated for future multidimensional magneto-hydrodynamics
simulations in the supernova context.
Hydrodynamics Simulations
The hydrodynamic effort has matured, and a new parallel MHD code (with
P. Arras and S. Wong) and out-of-core cosmological hydrocode (with
H. Trac) are now in production mode. Five papers were submitted on this
topic over the year, covering the methodology, the Sunyaev-Zeldovich
effect, and black hole accretion.
Infrastructure
Efforts on the infrastructure have been very successful, with the very
efficient acquistion, installation, and operation of the McKenzie cluster.
This 536 processor economical beowulf cluster was first conceived in
September 2002, with vendor negotiations through November. The machine
was delivered and installed in December, and by January was running
production science code as the fastest computer in Canada. The low
cost and fast installation was made possible through the efforts of a
key innovative team of R. Humble, C. Loken, P. Martin and J. Dubinski.
This success is now used to leverage an new generation machine through
a CFI proposal, which could bring Canada to the top three scientifc
computing nations in the world.
Numerical Studies of Braneworld Dynamics
Working with Johannes Martin, Andrei Frolov, Lev Kofman, and Marco
Peloso of CITA, Felder developed a program for calculating the time
evolution of a braneworld system. The program self-consistently solves
the Einstein equations in the bulk and junction conditions on the
branes. Using this code they were able to show that such systems will
generically tend to have multiple metastable states corresponding to
different effective cosmological constants on the brane. A transition
from such a metastable state to the ground state could account for the
occurrence and end of inflation. This program is being made publicly
available under the name BRANECODE.
Dusty Protoplanetary Disks
Robin Humble works with James Murray (Leicester, Swinburne) and Sarah
Maddison (Swinburne) on protoplanetary dusty disks. The 3D non-linear
Navier-Stokes equations with two fluid phases (dust and gas) are solved
numerically in the protoplanetary disk. The dynamics of 10 micron and
larger dust grains are followed as they migrate and grow in size. Grain
growth means varying the magnitude of the drag forces between gas and
dust, and can also mean varying the form of the drag equations
themselves. Star, planet, and gas and dust self-gravity are also
included in the parallel smoothed particle hydrodynamics (SPH) code.
Resolving turbulent dust lofting and gravitational and turbulent drag
instabilities are current focus areas. A bonus of the Lagrangian
particle technique means it is trivial to track thermal and accretion
histories of dust grains. This may (one day) be used to determine
chemical compositions of planets.
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