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As the supernova cosmologists train their telescopes to the distant
explosions in the sky, I consider the less destructive explosions
coming out of the boxes on our desks. A major computational effort is
underway to develop detailed simulations of the thermonuclear
disruption of a carbon/oxygen white dwarf in a Type Ia supernova
(SN~Ia). By calculating synthetic light curves, spectra and
spectropolarization for a large number of such models, we are
constructing a theoretical counterpart to the growing observational
database of SNe~Ia. The theory, by specifying the physical parameters
affecting the luminosity of SNe~Ia, can play a major role in helping
limit the intrinsic dispersion and evolutionary biases of concern to
supernova cosmology experiments. In the first part of this talk, I
explore the diversity of SNe~Ia using a comprehensive grid of
parameterized 1-dimensional models. Most of the models lie "outside
the box" occupied by normal observed SNe~Ia, indicating that nature
realizes only a small subset of the theoretically conceivable
explosions. By examining suitable subsets of the models, we are able
to specify the physics underlying the important relationship between
SN~Ia peak luminosity and light curve width, as well as identify those
factors leading to deviation from it. In the second part of the talk,
I discuss recent efforts to develop realistic multi-dimensional models
that explode in a healthy way "out of the box", i.e., without any ad
hoc manipulation of parameters. Such models predict substantial
asymmetries in the SN ejecta, which we find may contribute further to
the diversity of SNe~Ia.
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