Heterotic/Type II Duality in D=4 and String/String Duality

TL;DR

This paper explores the duality between heterotic and type II string theories in four dimensions, highlighting new features related to K3 fiber embeddings in Calabi-Yau threefolds and their geometric transitions.

Contribution

It reveals novel aspects of heterotic/type II duality in four dimensions, especially concerning K3 fiber embeddings and conifold transitions in Calabi-Yau manifolds.

Findings

Identification of new features in 4D duality beyond 6D vacuum structure

Analysis of K3 fiber embeddings in Calabi-Yau threefolds

Study of conifold transitions in hypersurfaces and complete intersections

Abstract

We discuss the structure of heterotic/type II duality in four dimensions as a consequence of string-string duality in six dimensions. We emphasize the new features in four dimensions which go beyond the six dimensional vacuum structure and pertain to the way particular K3 fibers can be embedded in Calabi-Yau threefolds. Our focus is on hypersurfaces as well as complete intersections of codimension two which arise via conifold transitions.