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We present an unconventional approach for addressing the old cosmologicalconstant (CC) problem in a class of F(R,G) models of modified gravity. For a CCof arbitrary size and sign the corresponding cosmological evolution follows anexpansion history which strikingly resembles that of our real universe. Theeffects of the large CC are relaxed dynamically and there is no fine-tuning atany stage. In addition, the relaxation mechanism alleviates the coincidenceproblem. The upshot is that a large cosmological constant and the observedcosmic expansion history coexist peacefully in the Relaxed Universe. This modeluniverse can be thought of as an interesting preliminary solution of thecosmological constant problem, in the sense that it provides a successfuldynamical mechanism able to completely avoid the fine-tuning problem (thetoughest aspect of the CC problem). However, since the Relaxed Universe isformulated within the context of modified gravity, it may still suffer of someof the known issues associated with these theories, and therefore it can beviewed only as a toy-model proposal towards a final solution of the CC problem.

The Relaxed Universe: towards solving the cosmological constant problem dynamically from an effective action functional of gravity