The SO(32) heterotic string can be obtained from the type IIB string by gauging a discrete symmetry that acts as (−1) FL on the perturbative string states and reverses the parity of the D-string. Consistency requires the presence of 32 NS 9-branes – the S-duals of D9-branes – which give SO(32) Chan-Paton factors to open D-strings. At finite string coupling, there are SO(32) charges tethered to ...

A new “non-standard” quantization of the universal enveloping algebra of the split (natural) real form so(2, 2) of D2 is presented. Some (classical) graded contractions of so(2, 2) associated to a Z2 × Z2 grading are studied, and the automorphisms defining this grading are generalized to the quantum case, thus providing quantum contractions of this algebra. This produces a new family of “non-st...