Physical Spectra in String Theories --- BRST Operators and Similarity Transformations

TL;DR

This paper reviews similarity transformations linking different string theory backgrounds, exploring their structure through topological conformal algebra and gauge symmetry, enhancing understanding of string theory equivalences.

Contribution

It provides a systematic analysis of similarity transformations in string theories, connecting different backgrounds via algebraic and gauge symmetry perspectives.

Findings

Examples of similarity transformations between string backgrounds

Structural insights from topological conformal algebra

Role of gauge symmetry in transformations

Abstract

Several examples of similarity transformations connecting two string theories with different backgrounds are reviewed. We also discuss general structure behind the similarity transformations from the point of view of the topological conformal algebra and of the non-linear realization of gauge symmetry.