When a Rio audience booed Gerald Thomas’ reworking of Wagner’s “Tristan und Isolde,” he went up on stage and dropped his pants, mooning the crowd. “Now Mr. Thomas, the eternal enfant terrible of Brazilian theater, is paying the price. Acting on a complaint filed by the local chief of police, prosecutors have charged him with public indecency, and on Nov. 11 he is scheduled to appear before a judge who will decide whether there are grounds to proceed with the case.”