Vacuum polarization in a cosmic string spacetime induced by flat   boundary
  In this paper we analyze the vacuum expectation values of the field squared and the energy-momentum tensor associated to a massive scalar field in a higher dimensional cosmic string spacetime, obeying Dirichlet or Neumann boundary conditions on the surface orthogonal to the string. 
Eug\^enio R. Bezerra de Mello and Aram A. Saharian
hep-th