I've used the following notation in a report:
$G\boldsymbol{w}\in\mathcal{H}_2\,\forall\boldsymbol{w}\in\mathcal{H}_2 $
In other words $G$ projects $\boldsymbol{w}$ back into the same set. But this notation doesn't feel right. Is this correct or could somebody suggest better / clearer / more appropriate notation?