Marilyn Stasio Theater Critic In a radical departure from his usual intellectually esoteric style, Tom Stoppard’s new play is an intensely personal family drama. “Leopoldstadt,” which takes its name from the Jewish quarter of Vienna, doesn’t concern itself with quantum mechanics, metaphysical mysteries, Heisenberg’s Uncertainty Principle or Fermat’s Last Theorem — all topics the playwright has tackled in previous plays. But because it follows the disintegrating fortunes of a close-knit Jewish family (and their goyish relatives by marriage), it does deal, in its way, with chaos theory. The set (Richard Hudson, with a shout-out to the props team), costumes (Brigitte Reiffenstuel) and especially the lighting design (Neil Austin) bathe the first scene in an aura of domestic harmony. It’s 1899 and almost Christmas in Vienna. Everyone in the tastefully furnished Merz household appears to be approaching the 20th century with glad hearts. The family trade is prospering, the men are successful businessmen and academics, the women are smart and articulate and the children are well-behaved.