Infinite-dimensional algebras in dimensionally reduced string theory

TL;DR

This paper explores the algebraic structures arising from dimensionally reduced string theory on a torus, revealing affine Kac-Moody symmetries and discrete transformations in the effective Lagrangians.

Contribution

It demonstrates the emergence of affine $ ext{O}(2,2)$ Kac-Moody algebras with central extensions from duality symmetries in reduced string backgrounds.

Findings

Identification of two effective Lagrangians with $SL(2)/U(1)$ sigma-models.

Emergence of affine $ ext{O}(2,2)$ Kac-Moody algebra with a central term.

Existence of discrete symmetries relating different field configurations.

Abstract

We examine 4-dimensional string backgrounds compactified over a two torus. There exist two alternative effective Lagrangians containing each two $SL(2)/U(1)$ sigma-models. Two of these sigma-models are the complex and the K\"ahler structures on the torus. The effective Lagrangians are invariant under two different $O(2,2)$ groups and by the successive applications of these groups the affine $\widehat{O}(2,2)$ Kac-Moody is emerged. The latter has also a non-zero central term which generates constant Weyl rescalings of the reduced 2-dimensional background. In addition, there exists a number of discrete symmetries relating the field content of the reduced effective Lagrangians.