Casimir force induced on a plane by an impenetrable flux tube of finite   radius
  A perfectly reflecting (Dirichlet) boundary condition at the edge of an impenetrable magnetic-flux-carrying tube of nonzero transverse size is imposed on the charged massive scalar matter field which is quantized outside the tube on a plane which is transverse to the tube. We show that the vacuum polarization effects outside the tube give rise to a macroscopic force acting at the increase of the tube radius (if the magnetic flux is held steady). 
V.M. Gorkavenko, Yu.A. Sitenko, O.B. Stepanov
hep-th