Physical state representations and gauge fixing in string theory

Abstract

We re-examine physical state representations in the covariant quantization of bosonic string. We especially consider one parameter family of gauge fixing conditions for the residual gauge symmetry due to null states (or BRST exact states), and obtain explicit representations of observable Hilbert space which include those of the DDF states. This analysis is aimed at giving a necessary ingredient for the complete gauge fixing procedures of covariant string field theory such as temporal or light-cone gauge.

New Covariant Gauges in String Field Theory

“…since the condition Qφ (0) = 0 reduces to L n φ (0) = 0 (n ≥ 1) if there is no ghost fields (c −n or b −n ) in φ (0) . It would be possible to take explicit basis of the set of states satisfying the condition Q|f = 0 as well as we have analyzed in the old covariant theory for the states satisfying L n |f = 0 (n ≥ 1) [15]. With such a basis of states, analysis of the a = ∞ gauge would become easier in various situations.…”