Boundary conditions in first quantization

In the BRST approach to first quantization, bosonic ghosts can cause ambiguities in the cohomology (and thus in second quantization). This paper shows how nonminimal terms give a general solution to this problem, avoiding the need for picture-changing operators. As examples, the authors consider spinning particles, superparticles, covariantized light cone bosonic string field theory, and NSR superstring field theory