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Sohaken Seminar: Hua Chen (Central China Normal University and Nagoya University)

Abstract: F(R) gravity is one of the successful extensions to General Relativity. It contains an additional dynamical scalar degree of freedom, which could be responsible for primordial and late-time accelerations. Starobinsky’s $R^2$ model has been proven successful in causing primordial inflation. On the other hand, viable dark energy (DE) models in F(R) gravity generally suffer from a weak curvature singularity, which requires higher curvature corrections, e.g., an $R^2$ term. Therefore, it is intriguing to combine inflation and DE using the same Lagrangian. As a result, the cosmic evolution after inflation, say reheating and radiation-dominated era, would be altered compared with the original $R^2$ inflation and Standard Model of Cosmology. In this talk, I shall first review inflation and DE in the framework of F(R) gravity. Utilizing the fluid approximation, I will introduce how the evolution in the early universe would be influenced (in Einstein frame) and compare the result with chameleon dark energy models in scalar-tensor theories.

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