THE AGE PROBLEM IN INHOMOGENEOUS UNIVERSES

Recent determinations of globular cluster ages imposes severe problems for the standard cosmological models. Before introducing a cosmological constant, other possibilities of solving the problem should be investigated carefully. In this paper, the backreactions of inhomogeneities in realistic, clumpy universes and their influence on age determinations are studied. Applying a recently developed approximation scheme, it is shown that the backreactions lead to an underestimation of the age of the universe as inferred from a measurement of today's Hubble parameter. Observations of the cosmic microwave background radiation impose constraints on the parameters. For a simple model within the framework of pancake theory for structure formation on a flat expanding background, it is shown that the age problem may be solved by taking into account the backreactions of inhomogeneities in an averaged sense. No cosmological constant is needed.