“A Serious Man” is the story of an ordinary man’s search for clarity in a universe where Jefferson Airplane is on the radio and “F-Troop” is on TV. It is 1967, and Larry Gopnik (Michael Stuhlbarg), a physics professor at a quiet Midwestern university, has just been informed by his wife Judith (Sari Lennick) that she is leaving him. She has fallen in love with one of his more pompous colleagues, Sy Ableman (Fred Melamed), who seems to her a more substantial person than the feckless Larry.