Surface configuration in R + μ 4/R gravity

We investigate the conditions on the additional constant μ in the so-called R + μ4/R theory of gravity, due to existence of different kinds of space-like surfaces in both weak field and strong field limits, and their possible correspondence to black hole event horizons. Adopting a Schwarzschild limit, we probe the behavior of μ in different contexts of radial and radial-rotational congruence of null geodesics. We show that these cases serve as correspondents to black hole horizons in some peculiar cases of study.