Correlation volume
= Correlation volume
{title2=$V_\xi\sim\xi^D$}
A volume over which order-parameter fluctuations are correlated. For one isotropic <correlation length> $\xi$, its scale is $\xi^D$; with anisotropic lengths it is the product of the appropriate directional lengths. A <Ginzburg criterion> compares fluctuations averaged over this volume with the squared mean <order parameter>.