Abstract: Generalized teleparallel gravity, also referred to as f(T) gravity, has
been recently proposed as an extended theory of gravitation able to give
rise to an accelerated expansion in a matter-only universe. The cosmic
speedup is driven by an effective torsion fluid whose equation of state
depends on the f(T) function entering the modified gravity Lagrangian.
We focus on two particular choices for f(T) which share the nice
property of emulating a phantom divide crossing as suggested by some
recent data. We check their viability, contrasting the predicted
background dynamics with the Hubble diagram as traced by both type Ia
supernovae and gamma ray bursts, the measurement of the rate expansion
H(z), the baryon acoustic oscillations at different redshifts, and the
cosmic microwave background radiation distance priors. Both f(T) models
turn out to be in very good agreement with this large data set, so we
also investigate whether it is possible to discriminate among them,
relying on the different growth factors.
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