Anomalies, Dualities, and Topology of D=6 N=1 Superstring Vacua

TL;DR

This paper explores various compactifications of Type I and heterotic string theories on K3 surfaces, revealing dualities, topological features, and anomaly cancellation mechanisms that deepen understanding of non-perturbative gauge fields in these models.

Contribution

It identifies and analyzes dualities between different string compactifications on K3, including topological novelties and anomaly cancellation, expanding the understanding of string vacua.

Findings

Dualities between Spin(32)/Z_2 and E8×E8 models on K3

Topological features in certain orbifold compactifications

Anomaly cancellation via extended Green-Schwarz mechanism

Abstract

We consider various aspects of compactifications of the Type I/heterotic $Spin(32)/\Z_2$ theory on K3. One family of such compactifications includes the standard embedding of the spin connection in the gauge group, and is on the same moduli space as the compactification of the heterotic $E_8\times E_8$ theory on K3 with instanton numbers (8,16). Another class, which includes an orbifold of the Type I theory recently constructed by Gimon and Polchinski and whose field theory limit involves some topological novelties, is on the moduli space of the heterotic $E_8\times E_8$ theory on K3 with instanton numbers (12,12). These connections between $Spin(32)/\Z_2$ and $E_8\times E_8$ models can be demonstrated by T duality, and permit a better understanding of non-perturbative gauge fields in the (12,12) model. In the transformation between $Spin(32)/\Z_2$ and $E_8\times E_8$ models, the strong/weak coupling duality of the (12,12) $E_8\times E_8$ model is mapped to T duality in the Type I theory. The gauge and gravitational anomalies in the Type I theory are canceled by an extension of the Green-Schwarz mechanism.