A special case of the BV formalism is the “standard” BRST formalism. It works for such theories as
Yang-Mills/QCD, and also for the bosonic string worldsheet theory
and the RNS superstring.
The most important property of such theories is the existence of a fermionic “BRST symmetry”
which is nilpotent off-shell (i.e. nilpotent without using the equations of motion).
Here we will briefly review these standard BRST theories, and show that in this case exists a natural
choice for .