= Branch weight
{title2=$w_i=\|\Psi_i\|^2$}
For an orthogonal decomposition $\Psi=\sum_i\Psi_i$, the squared <norms> add to the total <norm>. Refining one component into orthogonal subcomponents preserves its total weight by the <Pythagorean theorem>. In an Everettian account these weights are candidates for governing <probabilities>, rational credences or decisions; the algebra alone does not select which interpretive role is justified. Counting arbitrarily refined components is not the same measure.<Quantum Probability and Decision Theory, Revisited by David Wallace>[sections 4–5]{ref}
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