A tart and pouty perfect 10. The one negative element of David Auburn’s Proof is the calculated melodrama he factors into his Broadway play on genius and madness. Parker, 36, solves that problem with strength and wit of unparalleled shrewdness, changing cheap sentiment into rich feeling. Her Catherine, the daughter of a strange mathematician, is girly and surly and down and trying to figure out how to apply her own estimable intelligence to fill in the blank left by her father’s death. Parker’s posture is integral to the turn — a sprawling slouch that congruously expresses vibrant tension and depressed funk. She slacks, slumps, and works up to a heartrending rage. Because there is zero showiness to her show and because she is infinitely inventive, she therefore earns our ardor.