  In the conventional BV description of string field theory, the string field
Phi is split as Phi = Psi+Psi* where Psi includes all states with ghost number
less than or equal to G and describes the spacetime fields, and Psi* includes
all states with ghost number >G and describes the spacetime antifields. A new
approach is proposed here in which separate string fields Psi and Psi* of
unrestricted ghost number describe the spacetime fields and antifields. The
string antifield Psi* is constrained to satisfy Psi* = {\partial L}/{\partial(Q
Psi)} where L is the BV Lagrangian and Q is the worldsheet BRST operator. Dirac
antibrackets are defined using this constraint, and the resulting description
is equivalent to the conventional BV description for open and closed bosonic
string field theory. For open superstring field theory, this constrained BV
description is much simpler than the conventional BV description and allows the
BV action to be expressed in the same WZW-like form as the classical action.
