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In this brief summary I will concentrate on the values of the cosmological parameters. The other key questions in cosmology today concern the nature of the dark matter and dark energy, the origin and nature of the primordial inhomogeneities, and the formation and evolution of galaxies. I have been telling my theoretical cosmology students for several years that these latter topics are their main subjects for research, since determining the values of the cosmological parameters is now mainly in the hands of the observers.

In discussing cosmological parameters, it will be useful to distinguish between two sets of assumptions: (a) general relativity plus the assumption that the universe is homogeneous and isotropic on large scales (Friedmann-Robertson-Walker framework), or (b) the LambdaCDM family of models. The LambdaCDM models assume that the present matter density Omegam plus the cosmological constant (or its equivalent in ``dark energy'') in units of critical density OmegaLambda = Lambda / (3 H02) sum to unity (Omegam + OmegaLambda = 1) to produce the flat universe predicted by simple cosmic inflation models. The LambdaCDM family of models was introduced by Blumenthal et al. (1984), who worked out the linear power spectra P(k) and a semi-analytic treatment of structure formation compared to the then-available data. We did ths for the Omegam = 1, Lambda = 0 ``standard'' cold dark matter (CDM) model, and also for the Omegam = 0.2, OmegaLambda = 0.8 LambdaCDM model. In addition to Omegam + OmegaLambda = 1, these LambdaCDM models assumed that the primordial fluctuations were Gaussian with a Zel'dovich spectrum (Pp(k) = Akn, with n = 1), and that the dark matter is mostly of the cold variety.

The table below summarizes the current observational information about the cosmological parameters. The quantities in brackets have been deduced using at least some of the LambdaCDM assumptions. The rest of this paper discusses these issues in more detail. But it should already be apparent that there is impressive agreement between the values of the parameters determined by various methods.

Table 1. Cosmological Parameters [results assuming LambdaCDM in brackets]

Hubble parameter H0 = 100 h = km s-1 Mpc-1 , h = 0.65 ± 0.08
Age of universe t0 = 9-16 Gyr (from globular clusters)
= [9-17 Gyr]
Baryon density Omegab h2 = 0.019 ± 0.001 (from D/H)
> [0.015 from Lyalpha forest opacity]
Matter density Omegam = 0.4 ± 0.2 (from cluster baryons)
= [0.34 ± 0.1 from Lyalpha forest P(k)]
= [0.4 ± 0.2 from cluster evolution]
> 0.3 (2.4 sigma, from flows)
approx 3/4 OmegaLambda - 1/4 ± 1/8 from SN Ia
Total density Omegam + OmegaLambda approx 1 ± 0.3 (from CMB peak location)
Dark energy density OmegaLambda = 0.8 ± 0.3 (from previous two lines)
< 0.73 (2sigma) from radio QSO lensing
Neutrino density Omeganu gtapprox 0.001 (from Superkamiokande)
ltapprox [0.1]

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