The Exceptional Sigma Model

TL;DR

This paper constructs the exceptional sigma model, a string theory in extended spacetime, demonstrating its symmetry properties, reduction to known string actions, and exploring couplings and dynamical tension.

Contribution

It introduces the exceptional sigma model, extending the doubled sigma model framework to include U-duality and exceptional field theory structures.

Findings

The model's Weyl-invariant Lagrangian is uniquely determined by symmetry.

It reduces correctly to 10D string Lagrangians.

Includes formulations with generalized dilaton and dynamical tension.

Abstract

We detail the construction of the exceptional sigma model, which describes a string propagating in the "extended spacetime" of exceptional field theory. This is to U-duality as the doubled sigma model is to T-duality. Symmetry specifies the Weyl-invariant Lagrangian uniquely and we show how it reduces to the correct 10-dimensional string Lagrangians. We also consider the inclusion of a Fradkin-Tseytlin (or generalised dilaton) coupling as well as a reformulation with dynamical tension.