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Y. Wang (The Univ. of Oklahoma)
Recent observational data of type Ia supernovae suggest that most of the energy in the universe is unknown. Type Ia supernovae are our best candidates for cosmological standard candles; they can potentially provide us with a unique probe into the nature of the dark energy in the universe. To assess the ability of current and future supernova data to constrain the properties of the dark energy, we allow its density to have arbitrary time-dependence, \rhoX(z). This leads to an equation of state for the dark energy, w(z)=pX(z)/\rhoX(z), which is a free function of redshift z. Due to the integrals and parameter degeneracies in the distance-redshift relations of standard candles, it is extremely difficult to derive the time-dependence of the dark energy density in a model-independent manner from realistic data.
We have constructed a powerful algorithm based on the weak energy condition (energy density of matter is nonnegative for any observer), which allows us to extract the time-dependence of the dark energy density from realistic data. We find that current type Ia supernova data are consistent with a cosmological constant, with large uncertainties at z>0.5. Supernova pencil beam surveys are essential in constraining the systematic uncertainties of supernovae as cosmological standard candles. We show that \rhoX(z)/\rhoX(z=0) can be measured reasonably well to about z=1.5 using type Ia supernova data from realistic future supernova pencil beam surveys, provided that the weak energy condition is imposed, and the systematic uncertainties of supernovae (for example, gravitational lensing and peak luminosity evolution) are properly modeled.
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The author(s) of this abstract have provided an email address for comments about the abstract: wang@mail.nhn.ou.edu