The producers of a Broadway show that formerly starred Jeremy Piven filed a union grievance against the actor last week for violating his contract. Piven left the show suddenly last month, saying he had been diagnosed with mercury poisoning from eating sushi. That claim was met with skepticism by some, including the play’s author, David Mamet, who remarked that Piven had quit acting “to pursue a career as a thermometer.” Piven’s spokeswoman called the grievance charges “absurd and outrageous.”