Transition redshift in f(T) cosmology and observational constraints

We extract constraints on the transition redshift z(tr), determining the onset of cosmic acceleration, predicted by an effective cosmographic construction, in the framework of f(T) gravity. In particular, employing cosmography we obtain bounds on the viable f(T) forms and their derivatives. Since this procedure is model independent, as long as the scalar curvature is fixed, we are able to determine intervals for z(tr). In this way we guarantee that the Solar-System constraints are preserved and, moreover, we extract bounds on the transition time and the free parameters of the scenario. We find that the transition redshifts predicted by f(T) cosmology, although compatible with the standard Lambda CDM predictions, are slightly smaller. Finally, in order to obtain observational constraints on f(T) cosmology, we perform a Monte Carlo fitting using supernova data, involving the most recent Union 2.1 data set.