Dynamical twisting and the b ghost in the pure spinor formalism

After adding an RNS-like fermionic vector \psi^m to the pure spinor formalism, the non-minimal b ghost takes a simple form similar to the pure spinor BRST operator. The N=2 superconformal field theory generated by the b ghost and the BRST current can be interpreted as a “dynamical twisting” of the RNS formalism where the choice of which spin half \psi^m variables are twisted into spin 0 and spin 1 variables is determined by the pure spinor variables that parameterize the coset SO(10)/U(5).