Surprises in Open-String Perturbation Theory

TL;DR

This paper explores surprising features in open-string perturbation theory, including anomalies, singularities, and the role of boundaries and branes, highlighting their connection to string dualities and non-perturbative phenomena.

Contribution

It uncovers novel singularities and consistency mechanisms in open-string models, emphasizing the significance of boundaries and branes in string theory's perturbative and non-perturbative regimes.

Findings

Variable antisymmetric tensors ensure consistency via Green-Schwarz cancellations.

A new type of singularity appears in moduli spaces of open-string models.

Open-string features relate to boundaries and branes, influencing string dualities.

Abstract

The perturbative analysis of models of open and closed superstrings presents a number of surprises. For instance, variable numbers of antisymmetric tensors ensure their consistency via generalized Green-Schwarz cancellations and a novel type of singularity occurs in their moduli spaces. All these features are related, in one way or another, to the presence of boundaries on the world sheet or, equivalently, of extended objects (branes) interacting with the bulk theory in space time. String dualities have largely widened the interest in these models, that exhibit a wealth of generic non-perturbative features of String Theory.