= Cut norm
{title2=$\|H\|_{\mathrm{cut}}=\max_{A,B}|\mathbb E H1_A1_B|$}
For a <real-valued function> $H$ on a nonempty finite <Cartesian product> $X\times Y$, its normalized cut norm is the maximum of $|\mathbb E_{x,y}H(x,y)1_A(x)1_B(y)|$ over $A\subseteq X,B\subseteq Y$. It measures all rectangular subset discrepancies. The convention using arbitrary test functions bounded by one is equivalent within a factor of four, by decomposing their positive and negative parts into <indicator functions>.
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