Abrikosov parameter
= Abrikosov parameter
{c}
{title2=$\beta_A=\langle|\psi|^4\rangle/\langle|\psi|^2\rangle^2$}
A measure of spatial nonuniformity in the <order parameter>, with averages taken over one lattice cell. Set $X=|\psi|^2$. Then
$$
\beta_A=1+\frac{\operatorname{Var}(X)}{\langle X\rangle^2}\geq1.
$$
Equality requires uniform $|\psi|^2$, so a nonconstant core pattern costs more in the quartic term than a uniform amplitude with the same mean squared amplitude. This identity alone does not compare two different vortex arrays: their admissible profiles must also satisfy the field equations.