Torsion of Space-time in f(R) gravity
  In this paper, we first review some aspects of the f(R) gravity and then the concept of torsion of space-time due to metric-affine formalism in f(R) gravity is studied. Within this formalism in which the matter action is supposed to dependent on the connection, we achieve to interesting cases including non-zero torsion tensor. Then with the physical interpretation of torsion of space-time in high energy limit, the modified expression of Mach's principle in a very strong gravitational region is obtained. 
Majid Mohsenzadeh and Ebrahim Yusofi
physics.gen-ph gr-qc