We propose the finite-size scaling of correlation function in a finite system near its critical point. At a distance
r in the finite system with size
L, the correlation function can be written as the product of
∣r∣−(d−2+η) and its finite-size scaling function of variables
r/L and
tL1/ν, where
t=(T−Tc)/Tc. The directional dependence of correlation function is nonnegligible only when
∣r∣ becomes compariable with
L. This finite-size scaling of correlation function has been confirmed by correlation functions of the Ising model and the bond percolation in two-diemnional lattices, which are calculated by Monte Carlo simulation. We can use the finite-size scaling of correlation function to determine the critical point and the critical exponent
η.
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.
We progress finite-size scaling in systems with free boundary conditions above their upper critical dimension, where in the thermodynamic limit critical scaling is described by mean-field theory. Recent works show that the correlation length is not bound by the system's physical size, a belief that long held sway. Instead, two scaling regimes can be observed — at the critical and pseudo-critical temperatures. We demonstrate that both are manifest for free boundaries. We use numerical simulations of the d = 5 Ising model to analyse the magnetization, susceptibility, magnetization Fourier modes and the partition function zeros. While some of the response functions hide the dual finite-size scaling, the precision enabled by the analysis of Lee–Yang zeros allows this be brought to the fore. In particular, finite-size scaling of leading zeros at the pseudo-critical point confirms recent predictions coming from correlations exceeding the system size. This paper is dedicated to Jaroslav Ilnytskyi on the occasion of his 60th birthday.