Reconstructing cosmic acceleration from modified and nonminimal gravity: The Yang-Mills case

A variant of the accelerating cosmology reconstruction program is developed for f(R) gravity and for a modified Yang-Mills/Maxwell theory. Reconstruction schemes in terms of e-foldings and by using an auxiliary scalar field are developed and carefully compared, for the case of f(R) gravity. An example of a model with a transient phantom behavior without real matter is explicitly discussed in both schemes. Further, the two reconstruction schemes are applied to the more physically interesting case of a Yang-Mills/Maxwell theory, again with explicit examples. Detailed comparison of the two schemes of reconstruction is presented also for this theory. It seems to support, as well, physical nonequivalence of the two frames. © 2010 The American Physical Society.