QCD-Scale f(R) Theories: Local and Cosmological Constraints

In this Thesis we investigate the phenomenology of two QCD-scale modified gravity models. The first f(R) modified gravity model is the square-root modified model , which is motivated by q-theory. The second f(R) model which is investigated in this Thesis is a modified gravity model that is relevant in the high-curvature regime, motivated by the form of the one-loop effective action arising from gluons in curved spacetime.