Notes on f(T) theories

The cosmological models based on teleparallel gravity with nonzero torsion are considered. To investigate the evolution of this theory, we consider the phase-space analysis of the f(T) theory. It shows when the tension scalar can be written as an inverse function of x where x - rho e/(3m(pl)(2)H(2)) and T - g(x), the system is an autonomous one. Furthermore, the omega(e) - omega(e)' phase analysis is given out. We perform the dynamical analysis for the models f(T) beta T ln(T/T-0) and f(T) = alpha m(pl)(2)(-T/m(pl)(2))(n) particularly. We find that the universe will settle into de-Sitter phase for both models. And we have examined the evolution behavior of the power law form in the omega(ep) - omega(ep)' plane.