Topical Oral, Tuesday, May 27, 2003, 8:30-10:00am, 10:45am-12:30pm, 2:00-3:30pm and 3:45-5:30pm, 205/206

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*Y. Wang (Univ. of Oklahoma)*

Type Ia supernovae (SNe Ia) provide us with a unique probe
into the nature of dark energy in the universe. Different
dark energy models can be differentiated phenomenologically
by the different time dependences of the dark energy density
\rho_{X}, or, alternatively, by the dark energy equation of
state w_{X}. Wang & Garnavich (2001, ApJ, 552, 445) have
shown that parametrizing the dark energy density \rho_{X} as
an arbitrary function of redshift offers some useful
advantages when used instead of the more familiar w_{X}
formulation. In particular, the time variation of \rho_{X}
can be determined from data with smaller uncertainty than
that of w_{X}. This is because \rho_{X} is on the same
footing as the matter density fraction \Omega_{m} in making
theoretical predications for the observables, while w_{X}
must be integrated over z to obtain \rho_{X} before
comparison with data can be made.

In order to determine the time dependence of the dark energy
density \rho_{X}, it is important that the supernova survey
be optimized for detecting large numbers of supernovae at
the highest possible redshifts (Wang & Lovelace 2001, ApJ,
562, L115). A supernova pencil beam survey on a dedicated
telescope (Wang 2000, ApJ, 531, 676, astro-ph/9806185)
provides the most efficient method to obtain the largest
possible number of supernovae at high redshifts. These can
be supplemented by surveys of nearby supernovae to constrain
dark energy. I will show that data from an optimized
supernova pencil beam survey, such as that planned by the
proposed SNAP mission, should allow us to determine the
basic time dependence of the dark energy density \rho_{X}
(Wang et al. 2003, astro-ph/0302064). This would allow us to
differentiate among many different classes of dark energy
models.

The observational detection of the time variation (or
invariance) of the dark energy density \rho_{X} would be an
important landmark in particle physics and cosmology.

If you would like more information about this abstract, please follow the link to http://www.nhn.ou.edu/~wang/. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

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Bulletin of the American Astronomical Society, **35** #3

© 2003. The American Astronomical Soceity.