Tom Stoppard, whose 1993 comedy Arcadia is being revived by Bedlam, turned 86 last summer and, to the extent discernible from afar, he’s going strong. A year ago Stoppard was in New York for the premiere of Leopoldstadt, an emotionally charged, multigenerational epic. Set in Vienna during the Holocaust, that late-career masterwork proved surprising even for a playwright who’s known to avoid doing anything twice. When it was new, Arcadia was also a surprise. It represents the dramatist in midcareer, his imagination careening among a wild assortment of topics: English landscape gardening, quantum physics, the theory of deterministic chaos, and the peril for researchers of what’s inscrutable in the historical record (as, for example, gaps in the biography of George Gordon, Lord Byron, an important offstage character).