= Fisher scaling relation
{c}
{title2=$\gamma=(2-\eta)\nu$}
The <correlation-function susceptibility sum rule> and $G(r)=r^{-(D-2+\eta)}f_G(r/\xi)$ give $\chi_s\propto\xi^{2-\eta}$ when $f_G(0)$ is finite, its large-distance tail is integrable and $\eta<2$. With <correlation-length critical exponent> $\nu$, this gives the displayed relation for the <magnetic-susceptibility critical exponent>. Microscopic distances contribute a regular background rather than the divergent critical power.
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