Hellinger affinity
= Hellinger affinity
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{title2=$\int\sqrt{pq}\,d\mu$}
The <Hellinger affinity> of dominated <probability measures> is the integral of the geometric mean of their <probability density functions>. It lies in $[0,1]$ by <Cauchy-Schwarz inequality>. The unnormalized squared <Hellinger distance> is $2-2$ times this affinity; this identity makes the relation with <relative entropy> particularly simple.