Lecture 14 Mar

Today we talked about material Z-bach focuses on in Chapter 17. We explained in detail T-duality on closed and open strings propagating on R^1,8 x S¹, flat spacetime times a circle. The important bits were: (a) solving the string wave equation with oscillators plus pieces linear in tau and linear in sigma and deriving the mass formula; (b) physical properties of KK and winding modes; (c) T-duality as switching momentum with winding and inverting the circle radius in string units; (d) enhanced SU(2) gauge symmetry at the self-dual radius; (e) T-duality as changing D-brane dimension because it swaps D and N conditions with one another; (f) D-branes, open strings and Wilson lines.  T-duality: the first duality