M.Horta¸csu

We extend the work done for cosmic strings on the perturbative calculation of vacuum polarization of a massless field in the space-time of multiple cosmic strings and show that for a more general class of locally flat metrics the one loop calculation do not introduce any new divergences to the VEV of the energy of a scalar particle or a spinor particle. We explicitly perform the calculation for the configuration where we have one cosmic string in the presence of a dipole made out of cosmic strings both for the scalar and the spinor cases. PACS number is 98.80 Cq 1 Introduction Extensive work has been done on cosmic strings =1 and other topological defects. A remarkable property of the field theoretical calculations using cosmic strings as background is the existence of a finite contribution to the energy of a scalar particle due to the presence of the cosmic string =2 . In a beautiful paper =3 A.N. Aliev showed that there is an intricate cancellation mechanism in the cosmic st..