Gravitational Red Shift And Time Delay Of Radar Echo In F(R)-Gravity

The cosmological models are based on the theory of gravitation and one of the basic assumptions of ?CMD-model(the standard cosmological model) is that,space, time and matter in the universe are connected by Einstein's general relativity. ?CDM is a Big Bang model which includes inflation. It shows us that 95% of the total mass-energy density of the current universe is composed of dark matter and dark energy. The main observational facts that support the existence of dark matter and dark energy are, accelerating expansion of the universe, gravitational lens and rotation curve of the galaxy. We can correct the Einstein gravity theory so that the theoretical results are consistent with the observed facts, and we do not add unknown dark matter and dark energy in the universe. f(R) theory is one of them. It is obtained by extending the Ricci scalar in the Hilbert-Einstein Lagrange density to a more general function f(R). Y. Sobouti proposes an action-based f(R) modification of Einstein's gravity, which admits a similar Schwarzschild metric. A test star moving in such a space-time acquires a constant asymptotic speed at large distances. There are two classical tests of Einstein's theory which are gravitational red shift of spectral lines and time delay of radar echo passing the sun, we shall calculate them in the f(R) gravity and show that the results are consistent with the experimental observation data.