Cutoff and lattice effects in the rho(4) theory of confined systems

We study cutoff and lattice effects in the O(n) symmetric phi(4) theory for a d-dimensional cubic geometry of size L with periodic boundary conditions . In the large-n limit above T-c, we show that phi(4) field theory at finit e cutoff ii predicts the nonuniversal deviation similar to (Lambda L)(-2) f rom asymptotic bulk critical behavior that violates finite-size scaling and disagrees with the deviation similar to e(-cL) that we find in the phi(4) lattice model. The exponential size dependence requires a non-perturbative treatment of the phi(4) model. Our arguments indicate that these results sh ould be valid for general n and d > 2.