The Nappi-Witten example and gravitational waves

TL;DR

This paper discusses how the Nappi-Witten model, built from a specific non-semisimple group, exemplifies a broader principle where gravitational wave backgrounds lead to anomaly cancellation in Wess-Zumino-Witten models.

Contribution

It demonstrates that the anomaly cancellation in the Nappi-Witten model is a specific case of a general result applicable to gravitational wave backgrounds.

Findings

Anomaly vanishing in Nappi-Witten model explained by gravitational wave properties

Construction method of the associated metric detailed

Supports broader applicability of gravitational wave backgrounds in string theory

Abstract

The vanishing of the anomaly in the recent example of Nappi and Witten, constructed from the Wess-Zumino-Witten model based on a certain non-semisimple group, follows from a more general result valid for gravitational waves. The construction of the metric is explained.}