Two Double String Theory Actions: Non-Covariance vs. Covariance

TL;DR

This paper compares two formulations of bosonic string theory that make T-duality manifest, one non-covariant and one covariant, demonstrating their equivalence and highlighting different approaches to symmetry realization.

Contribution

It introduces and analyzes two models of bosonic string theory that explicitly incorporate T-duality, one non-covariant and one covariant, and proves their equivalence.

Findings

Both models successfully incorporate T-duality as a manifest symmetry.

The non-covariant model is based on chiral field Lagrangians with on-shell covariance.

The covariant model doubles target space coordinates, maintaining two-dimensional covariance.

Abstract

The aim of this work is to achieve a formulation of the bosonic string theory in which T-duality appears as a manifest symmetry. Two models exhibiting this property are discussed. The first is based on the stringy extension of the Floreanini-Jackiw Lagrangians for chiral fields and is characterized by the loss of manifest covariance on the world-sheet, recovered on mass-shell. The second model exhibits two-dimensional covariance while doubling a priori the string coordinates in the target space. They are shown to be equivalent.