  Complete set of cylindrical modes is constructed for the electromagnetic
field inside and outside a cylindrical shell in the background of $(D+1)$%
-dimensional dS spacetime. On the shell, the field obeys the generalized
perfect conductor boundary condition. For the Bunch-Davies vacuum state, we
evaluate the expectation values (VEVs) of the electric field squared and of the
energy-momentum tensor. The shell-induced contributions are explicitly
extracted. In this way, for points away from the shell, the renormalization is
reduced to the one for the VEVs in the boundary-free dS bulk. As a special
case, the VEVs are obtained for a cylindrical shell in the $(D+1)$%
-dimensional Minkowski bulk. We show that the shell-induced contribution in the
electric field squared is positive for both the interior and exterior regions.
The corresponding Casimir-Polder forces are directed toward the shell. The
vacuum energy-momentum tensor, in addition to the diagonal components, has a
nonzero off-diagonal component corresponding to the energy flux along the
direction normal to the shell. This flux is directed from the shell in both the
exterior and interior regions. For points near the shell, the leading terms in
the asymptotic expansions for the electric field squared and diagonal
components of the energy-momentum tensor are obtained from the corresponding
expressions in the Minkowski bulk replacing the distance from the shell by the
proper distance in the dS bulk. The influence of the gravitational field on the
local characteristics of the vacuum is essential at distances from the shell
larger than the dS curvature radius. The results are extended for confining
boundary conditions of flux tube models in QCD.
