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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 \rhoX, or, alternatively, by the dark energy equation of state wX. Wang & Garnavich (2001, ApJ, 552, 445) have shown that parametrizing the dark energy density \rhoX as an arbitrary function of redshift offers some useful advantages when used instead of the more familiar wX formulation. In particular, the time variation of \rhoX can be determined from data with smaller uncertainty than that of wX. This is because \rhoX is on the same footing as the matter density fraction \Omegam in making theoretical predications for the observables, while wX must be integrated over z to obtain \rhoX before comparison with data can be made.
In order to determine the time dependence of the dark energy density \rhoX, 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 \rhoX (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 \rhoX would be an important landmark in particle physics and cosmology.
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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.