JEREMY PIVEN IS BEST KNOWN as the venal, tantrum-throwing superagent Ari Gold on HBO's hit comedy "Entourage"; as an alumnus of the Piven Theater Workshop in Chicago, founded by his parents, Joyce and Byrne Piven; and as the center of a highly publicized 2009 breach-of-contract dispute after he left a Broadway production of "Speed-the-Plow" two months early, citing exhaustion and mercury poisoning.