We demonstrate that the standard O(n) symmetric φ4 field theory does not correctly describe the leading finite-size effects near the critical point of spin systems with periodic boundary conditions on a d-dimensional lattice with d>4. We show that these finite-size effects require a description in terms of a lattice Hamiltonian. For n →∞ and n=1, explicit results are given for the susceptibility and for the Binder cumulant. They imply that these quantities do not have the universal properties predicted previously and that recent analyses of Monte Carlo results for the five-dimensional Ising model are not conclusive.
We show numerically that correlation length at the critical point in the five-dimensional Ising model varies with system size
L as
L5∕4, rather than proportional to
L, as in standard finite-size scaling (FSS) theory. Our results confirm a hypothesis that FSS expressions in dimension
d greater than the upper critical dimension of 4 should have
L replaced by
Ld∕4 for cubic samples with periodic boundary conditions. We also investigate numerically the logarithmic corrections to FSS in
d=4.