Physical Review Letters
One—Scale-Factor Universality for Critical Phenomena
Donald D. Betts, Douglas S. Ritchie
Abstract
An extended universality hypothesis is proposed for critical phenomena in simple systems. The hypothesis implies the invariance of ${V}_{X}=\frac{{n}_{X}{q}_{X}{{K}_{C}}^{X}}{{g}_{X}{l}_{X}}$, where ${q}_{X}$ is the coordination number, ${{K}_{C}}^{X}$ is the dimensionless inverse critical temperature, and ${n}_{X}$, ${g}_{X}$, and ${l}_{X}$ are the universality scale factors. ${V}_{X}$ is an exact invariant for the two-dimensional $S=\frac{1}{2}$ Ising model and invariant to high precision for several three-dimensional models. For the spherical model, however, $\frac{{V}_{X}}{{l}_{X}}$ is an exact invariant.