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D. Huterer (Case Western Reserve University)
Around two-thirds of energy density in the universe is in the form of dark energy -. a spatially smooth component with negative pressure. Yet the nature and properties of dark energy are poorly understood. More accurate experimental measurements of the properties of dark energy, in particular its equation of state w, are crucial in order to make progress in theoretical and phenomenological understanding of this component. Here we show that a sample of several thousand type Ia supernovae with redshifts z\lesssim 2, as might be gathered by the proposed SNAP satellite, would serve as a powerful probe of dark energy. SNAP will constrain the equation of state to about 5%, independently of other cosmological probes and assuming only a flat universe. Even tighter constraints will be obtained using complementary measurements of matter energy density from, e.g., weak lensing and large-scale structure surveys. Moreover, with these complementary measurements SNAP can study the time (or redshift) evolution of w, which is perhaps the most challenging and important goal. This is only possible with the high-quality measurements of type Ia supernovae such as that provided by SNAP. We illustrate constraints on w(z) and on dark energy models that could be obtained using SNAP.