Traversable Wormholes and Time Machines in non-minimally coupled   curvature-matter $f(R)$ theories
  We obtain traversable wormhole and time machine solutions of the field equations of an alternative of gravity with non-minimally curvature-matter coupling. Our solutions exhibit a non-trivial redshift function and allow for matter that satisfy the dominant energy condition. 
Orfeu Bertolami, Ricardo Zambujal Ferreira
gr-qc astro-ph.CO hep-th