New Branches of String Compactifications and their F-Theory Duals

TL;DR

This paper explores new string compactification models with elliptic fibrations, analyzing their F-theory duals, gauge backgrounds, and transitions, revealing novel U(1) symmetries and instanton effects in heterotic and F-theory frameworks.

Contribution

It introduces new classes of string compactifications with different elliptic fibers, expanding the understanding of heterotic/F-theory duality and gauge symmetry structures.

Findings

Identification of new elliptic fiber choices leading to unbroken U(1) symmetries.

Evidence of E_d instanton effects in six-dimensional models.

Analysis of conifold transitions among different elliptic fiber realizations.

Abstract

We study heterotic $E_8\times E_8$ models that are dual to compactifications of F-theory and type IIA string on certain classes of elliptically fibered Calabi-Yau manifolds. Different choices for the specific torus in the fibration have heterotic duals that are most easily understood in terms of $E_8\times E_8$ models with gauge backgrounds of type $H\times U(1)^{8-d}$, where $H$ is a non-Abelian factor. The case with $d=8$ corresponds to the well known $E_8\times E_8$ compactifications with non-Abelian instanton backgrounds $(k_1,k_2)$ whose F-theory duals are built through compactifications on fibrations of the torus $\IP_2^{(1,2,3)}[6]$ over $\IF_n$. The new cases with $d < 8$ correspond to other choices for the elliptic fiber over the same base and yield unbroken $U(1)$'s, some of which are anomalous and acquire a mass by swallowing zero modes of the antisymmetric $B_{MN}$ field. We also study transitions to models with no tensor multiplets in $D=6$ and find evidence of $E_d$ instanton dynamics. We also consider the possibility of conifold transitions among spaces with different realization of the elliptic fiber.