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3.1.3. Type Ia Supernova Hubble Diagram

The type Ia supernova Hubble diagram now reaches z appeq 0.4-0.8. It can be used to infer the mass density parameter and the cosmological constant. As we discuss later (section 4.1) the observation favours a low Omega and a positive lambda. If we take their formal errors, Omega < 0.1 is allowed only at three sigma for a zero lambda universe (Riess et al. 1998; Perlmutter et al. 1999). A zero lambda open universe may not be excluded yet if some allowance is taken for systematic effects, but EdS geometry is far away from the observation. The best favoured value is approximately,

Equation 11 (11)