Hot for Teacher: Erin Weaver and Cody Nickell get excited about math in Aaron Posner’s new production of “Arcadia.” A few years after Larry David and Jerry Seinfeld dominated network television with their “show about nothing,” Tom Stoppard astonished the theater with a play about everything. More specifically, the mathematical conceits that govern the ultimate predictability of everything. Or don’t. Learned opinion varies about the math. Not so vis-à-vis the play: Arcadia was hailed…