Deviations of R 2 cosmology from the Einstein's General Relativity

The cosmological history of the universe in the R + R2 gravity is studied starting from the "very beginning"up to the present time. The primordial inflationary expansion of the universe is considered and it is shown that the gravitational particle production by the oscillating curvature, R(t), led to a consistent transition to the Friedmann cosmology, but the cosmological evolution in the early universe strongly differed from the standard one. It is shown that the effects of gravitational production of particles had a significant influence on the evolution of the universe.