Physical state representations and gauge fixing in string theory

TL;DR

This paper investigates physical state representations in covariant bosonic string quantization, exploring gauge fixing conditions and explicit observable Hilbert space representations, including DDF states, to aid in gauge fixing procedures.

Contribution

It introduces a one-parameter family of gauge fixing conditions and constructs explicit observable Hilbert space representations, enhancing understanding of gauge fixing in covariant string theory.

Findings

Explicit representations of observable Hilbert space including DDF states.

A family of gauge fixing conditions for residual gauge symmetry.

Insights toward complete gauge fixing in covariant string field 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.