Vacuum Expectation Value of the Spinor Massive field in the Cosmic   String Space-Time
  We found the contribution to the vacuum expectation value of the energy-momentum tensor of a massive Dirac field due to the conical geometry of the cosmic string space-time. The heat kernel and heat kernel expansion for the squared Dirac operator in this background are also considered and the first three coefficients were found in an explicity form. 
Valdir B. Bezerra and Nail R. Khusnutdinov