Scaling fields and universality of the liquid-gas critical point

We report an extensive Monte Carlo study of the density and energy fluctuations in a 2D Lennard-Jones fluid, within the grand-canonical ensemble. The results are analyzed within a finite-size-scaling theory incorporating the mixed character of the scaling fields that manifests particle-hole asymmetry. The limiting critical distribution of the density matches that of the magnetization in the 2D Ising model, illuminating the configurational basis of universality; the corrections to the limiting behavior contain an antisymmetric component which reflects the critical Ising energy operator, corroborating the anticipated structure of the scaling fields.