Dimensional reducers: Parisi-Sourlas super-rotations as BRST transformations

BRST [Becchi Rouet Stora Theory] cohomology is shown to imply Parisi-Sourlas [1979 Phys. Rev. Lett. 43,744] dimensional reduction in Minkowski space. Supersymmetric rotations into lightlike vectors are shown to be BRST transformations. We calculate their cohomology and thus give a non-perturbative demonstration of dimensional reduction in Minkowski space. We show how the BRST operator and its cohomology in the second quantised 'field' theory follows from the BRST operator in the first quantised 'particle' theory. (author)