= Wavevector selection rule for equivariant monomials
{title2=$\sum_j(p_j-q_j)k_j=k_\ell$}
An <equivariant dynamical system> can contain the <monomial> $\prod_jA_j^{p_j}\overline A_j^{q_j}$ in its $\ell$th <amplitude> equation only if its total <wavevector> equals the output <wavevector>. Its degree is $\sum_j(p_j+q_j)$. Thus an integer vector $d=p-q$ contributes at degree $N$ exactly when the <wavevector> equation holds, $\|d\|_1\leq N$, and $N-\|d\|_1$ is even. The extra even degree is supplied by factors $|A_j|^2$. This finite integer test distinguishes regular saturation terms from phase-sensitive <resonance> terms.
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