I have came across a notation I haven't seen before:
$$ \DeclareMathOperator*{\argmax}{\arg\,\max} W_{opt} = \argmax_{|W^TS_WW|=0} |W^TS_BW| $$
I am used to see a variable under $\argmax$, at most I have seen something like $\argmax_{W\in\mathbb{Z}}$.
Is this a way to put constraints? If we don't look at left hand side, it is kind of obscure that we are maximizing w.r.t. $W$. Is this a common notation that I am not aware of?
