New types of $f(T)$ gravity

Understand

Recently $f(T)$ theories based on modifications of teleparallel gravity where torsion is the geometric object describing gravity instead of curvature have been proposed to explain the present cosmic accelerating expansion.

• The field equations are always second order, remarkably simpler than $f(R)$ theories.
• In analogy to the $f(R)$ theory, we consider here three types of $f(T)$ gravity, and find that all of them can give rise to cosmic acceleration with interesting features, respectively.