On the strongly coupled heterotic string

TL;DR

This paper examines anomaly cancellation in the strongly coupled $E_8 imes E_8$ heterotic string, revealing new features and interpretations through duality and dimensional reduction.

Contribution

It provides a detailed analysis of anomaly cancellation conditions and introduces a new perspective based on heterotic string/fivebrane duality.

Findings

New anomaly cancellation features identified

Dimensional reduction clarifies physical couplings

Fivebrane language offers natural description of eleven-dimensional aspects

Abstract

We analyze in detail the anomaly cancellation conditions for the strongly coupled $E_8 \times E_8$ heterotic string introduced by Horava and Witten and find new features compared to the ten-dimensional Green-Schwarz mechanism. We project onto ten dimensions the corresponding Lagrangian of the zero-mode fields. We find that it has a simple interpretation provided by the conjectured heterotic string/fivebrane duality. The part which originates from eleven-dimensions is naturally described in fivebrane language. We discuss physical couplings and scales in four dimensions.