Cosmology of modified but second order gravity - General Relativity and Quantum CosmologyReport as inadecuate




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Abstract: This is a brief review of modified gravity cosmologies. Genericallyextensions of gravity action involve higher derivative terms, which can resultin ghosts and instabilities. There are three ways to circumvent this:Chern-Simons terms, first order variational principle and nonlocality. Weconsider recent cosmological applications of these three classes of modifiedgravity models, in particular to the dark energy problem. The viable parameterspaces can be very efficiently constrained by taking into account cosmologicaldata from all epochs in addition to Solar system tests and stabilityconsiderations. We make some new remarks concerning so called algebraicscalar-tensor theories, biscalar reformulation of nonlocal actions involvingthe inverse d-Alembertian, and a possible covariant formulation holographiccosmology with nonperturbative gravity.



Author: Tomi S. Koivisto

Source: https://arxiv.org/







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