Accelerated cosmological models in modified gravity tested by distant supernovae SNIa data

Recent type Ia supernova measurements and other astronomical observations suggest that our Universe is, at the present epoch, in an accelerating phase of evolution. While a dark energy of unknown form and origin is usually proposed as the most feasible mechanism for the acceleration, there appeared some generalizations of Einstein equations which could mimic dark energy. In this work we investigate observational constraints on a modified Friedmann equation obtained from the generalized Lagrangian L proportional to R-n minimally coupled with matter via the Palatini first-order formalism. We mainly concentrate on such restrictions of model parameters which can be derived from distant supernovae and baryon oscillation tests. We obtain confidence levels for two parameters (n, Omega(m,0)) and find, from combined analysis, that the preferred value of Omega(m,0) equals 0.3. For deeper statistical analysis and for comparison of our model with predictions of the Lambda CDM concordance model, one applies Akaike and Bayesian information criteria of model selection. Finally, we conclude that the Friedmann-Robertson-Walker model merged with a first-order nonlinear gravity survives SNIa and baryon oscillation tests.