Discrete Torsion, Quotient Stacks, and String Orbifolds

This is the writeup of a lecture given at the May Wisconsin workshop on mathematical aspects of orbifold string theory. In the first part of this lecture, we review recent work on discrete torsion, and outline how it is currently understood in terms of the B field. In the second part of this lecture, we discuss the relationship between quotient stacks and string orbifolds.