Papers
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Astrophysics papers
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Computer science papers
- Ph.D. Thesis, Indiana University
- My Ph.D. thesis (903KB).
Movies (mpeg format)
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Evolution of the Potential (264 KB)
- This movie shows the evolution of the potential
psi in the Standard Cold Dark Matter model;
psi plays the role of the gravitational
potential in the Newtonian limit. The square is a comoving 100 Mpc
across (1 pc = 3.3 light years).
The movie ends shortly after recombination, at
expansion factor 1/a = 1028,
or redshift z =1027.
The initial spatial
pattern of the potential is a statistical fractal owing to the
scale-invariant fluctuations we assume were generated by cosmic
inflation during the first femtosecond after the big bang. Acoustic
waves cause the potential fluctuations to spread and damp during
the radiation-dominated phase of the early universe. This evolution
of the potential produces the small angular scale features in the
CMB anisotropy map shown above.
The potential becomes almost constant after the universe becomes
matter-dominated.
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Evolution of the Density (1080 KB)
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This movie shows the evolution of the net density fluctuations
in the CDM model corresponding to the potential movie above. Green
corresponds to the mean density; blue regions are underdense and
red ones are overdense.
The density movie runs only half as long because once the universe
becomes matter-dominated at a redshift z=6000,
the density fluctuations
grow in proportion with the cosmic expansion factor (corresponding
to a constant gravitational potential), saturating the linear color
scale that we use.
The density pattern has finer
structure than the potential, to which it is related (via the
general relativistic form of the Poisson equation) by two spatial
derivatives.
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Galaxy Clusters (3.4 MB)
- This movie shows the evolution of a cluster
of fifty galaxies. The white particles are the
luminous cores of the galaxies; the red particles
are the dark matter halos of the galaxies; and
the blue particles form the dark matter cluster background.
The duration of the simulation covers 16 gigayear.
The field of view is roughly a megaparsec (3.26 million lightyears).
Due to dynamical friction and galatic interactions,
the largest galaxies fall to the center of the
cluster to form a dominant central galaxy through merging.
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Galaxy (0.5 MB)
- This is similar to the previous movie, except each galaxy
is represented as a single sphere.
Colors represent mass: blue is low mass, red is
high mass. The radius of each sphere is also proportionate to the mass.
The original simulation contained 40,000 particles and each galaxy
was comprised of a number of particles.
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100 Galaxy Simulation (2.7 MB)
- A 100-galaxy cluster simulated with 100,000 particles.
The white particles are the luminous cores of the galaxies; the red particles
are the dark matter halos of the galaxies. There was also a diffuse
dark matter intra-cluster background in the simulation, which is not
shown.
The duration of the simulation covers 10 gigayear.
The field of view is roughly a megaparsec (3.26 million lightyears).
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100 Galaxy Simulation (beginning) (0.8 MB)
- A fly-around of the initial state of the simulation.
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100 Galaxy Simulation (ending) (1.2 MB)
- A fly-around of the final state of the simulation.
Software
- TPM
(Tree-Particle-Mesh)
- Parallel code for simulating collisionless
cosmological dynamics.
- COSMICS
(Cosmological Initial Conditions) Package
- A package of fortran-77 programs useful for
cosmological modelling.
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