A free workshop performance of the first half of The Scarlet Professor, a new opera based on the celebrated 1960 arrest and trial of Smith College professor Newton Arvin, will take place on Sunday, June 7, at 3 p.m. in Buckley Recital Hall in the Arms Music Center at Amherst College. The semi-staged performance will be followed by a discussion with composer Eric Sawyer, librettist Harley Erdman and author Barry Werth, on whose book the opera is based.