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R. A. Daly (Penn State University), S. G. Djorgovski (California Institute of Technology)
Type Ia supernovae observations allow direct, model-independent determinations of the dimensionless expansion [E(z)] and acceleration [q(z)] rates of the universe as functions of redshift. The only assumptions required to obtain E(z) and q(z) from luminosity distances are that the universe is homogeneous and isotropic on large scales, and is spatially flat. Thus, E(z) and q(z) are obtained without specifying a gravity theory, or nature or properties of the dark energy. The values of E(z) and q(z) may then be combined to solve for the pressure, energy density, equation of state, potential energy density, and kinetic energy density of the dark energy as functions of redshift by specifying a theory of gravity.
Results obtained with a sample of 268 type Ia supernovae will be presented and compared with expectations in the LCDM model.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.