  We study the Casimir effect for a three dimensional system of ideal free
massive Bose gas in a slab geometry with Zaremba and anti-periodic boundary
conditions. It is found that for these type of boundary conditions the
resulting Casimir force is repulsive in nature, in contrast with usual
periodic, Dirichlet or Neumann boundary condition where the Casimir force is
attractive (Martin P. A. and Zagrebnov V. A., Europhys. Lett., 73 (2006) 15.).
Casimir forces in these boundary conditions also maintain a power law decay
function below condensation temperature and exponential decay function above
the condensation temperature albeit with a positive sign, identifying the
repulsive nature of the force.
