Non-Singular Modified Gravity Unifying Inflation with Late-Time Acceleration and Universality of Viscous Ratio Bound in F(R) Theory

摘要

The review of basic cosmological properties of four-dimensional F(R)-gravity, including FRW equations of motion and its accelerating solutions, generalized fluid and scalar-tensor representation of the theory is done. Cosmological reconstruction equation is written arid conditions for stability of cosmological solution are discussed. The overview of realistic F(R)-models unifying inflation with dark energy epoch is made. The avoidance of finite-time future singularities in such theories via the introduction of R~2-term is studied. New realistic noningular F(R)-gravity unifying early-time inflation with late-time acceleration is presented. The exit from inflationary era in such model may be caused by the gravitational scenario. It is demonstrated that five-dimensional F(R)-gravity considered as non-perturbative stringy effective action leads to universal relation for viscous bound ratio.