A Possible Way to Define an Effective Cosmological Constant in Scalar-Tensor Cosmologies
The cosmological constant has attained a leading role in recent researches in cosmology. We extend the cosmic no-hair theorem to non-minimally coupled theories of gravity where ordinary matter is also present in the form of a perfect fluid. To achieve this goal we give a set of conditions for obtaining the asymptotic de Sitter expansion independently of any initial data (no fine-tuning problem), that is, we introduce a time-dependent (effective) cosmological constant. Finally, we apply the results to some specific models.
KeywordsCosmological Constant Bianchi Identity Ordinary Matter Effective Cosmological Constant Repulsive Gravity
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