Vacuum Polarization in the Presence of Magnetic Flux at Finite   Temperature in the Cosmic String Background
  In this paper we analyse the vacuum polarization effect associated with the charged massless scalar field, in the presence of magnetic flux at finite temperature, in the cosmic string background. We consider a spacetime of an idealized cosmic string which presents a magnetic field confined in a cylindrical tube of finite radius. Two different situations are taken into account in our analysis: (i) a homogeneous field inside the tube and (ii) a magnetic field proportional to $1/r$. In these two cases, the axis of the infinitely long tube of radius $R$ coincides with the cosmic string. Specifically, we calculate the effects produced by the temperature in the renormalized vacuum expectation value of the square of the charged massless scalar field, $<\hat{\phi}^{\ast}(x)\hat{\phi}(x)>$. Therefore, in order to realize these analysis, we calculate the Euclidean Green function associated with this field in this background. 
J. Spinelly and E. R. Bezerra de Mello