Theoretical cosmology

Current understandings and unresolved questions in the field of theoretical big bang cosmology are discussed. Following a review of the fundamental assumptions and conventions of standard cosmological theory and of Newtonian gravitation and cosmology, general relativity and relativistic cosmology are introduced, and the analysis of observational data is discussed. Relativistic models not obeying the cosmological principle are considered, and attention is given to the nature and origin of the microwave radiation background, the thermal history of the universe and nucleosynthesis, the cosmological singularity, the gravitational constant as a field variable in the Brans-Dicke cosmology and cosmological models based on the Einstein-Cartan theory. The two-tensor theory of Isham, Salam and Strathdee (1971, 1973) and the conformally invariant theory of Hoyle and Narlikar (1972) are indicated, and the fate of perturbations of isotropic universes, galaxy formation and baryon symmetric cosmologies are considered