Abstract
We give a complete formulation of Poincare gauge theory, starting from the bre bundle formulation to the resultant Riemann-Cartan spacetime. We also introduce several diverse gravity theories descendent from the Poincare gauge theory. Especially, the cosmological e ect of the simple scalar-torsion (0+) mode in Poincare gauge theory of gravity is studied. In the theory, we treat the geometric e ect of torsion as an e ective quantity, which behaves like dark energy, and study the e ective equation of state (EoS) of the model. We concentrate on the two cases of the constant curvature solution and positive kinetic energy. In the former, we nd that the torsion EoS has di erent values corresponding to the stages of the universe. For example, it behaves like the radiation (matter) EoS of wr = 1=3 (wm = 0) in the radiation (matter) dominant epoch, while in the late time the torsion density is supportive for the accelerating universe. In the latter case of positive kinetic energy, we nd the (ane) curvature is not constant in general and hence requires numerical solution. Our numerical analysis shows that the EoS in general has an asymptotic behavior in the high redshift regime, while it could cross the phantom divide line in the low redshift regime. By further analysis of the Laurent series expansion, we nd that the early evolution of the torsion density T has a radiation-like asymptotic behavior of O(a?4) where a(t) denotes the scale factor, along with a stable point of the torsion pressure (PT ) and a density ratio PT =T ! 1=3 in the high redshift regime (z 0), this is di erent from the previous result in the literature. Some numerical illustrations are also demonstrated. We construct the extra dimension theory of teleparallel gravity by using di erential forms. In particular, we discuss the Kaluza-Klein and braneworld scenarios by direct dimensional reduction and specifying the shape of the bre. The FLRW cosmological scenario of the braneworld theory in teleparallel gravity demonstrates its equivalence to general relativity (GR) in the eld equations, namely they possess the same Friedmann equation.