Open F-branes

TL;DR

This paper explores F-theory with open Type I F-branes, unifying various string theories with N=1 supersymmetry and analyzing their symmetries, brane origins, and the specific case of D=3 F-theory.

Contribution

It introduces open Type I F-branes within F-theory, clarifies their relation to Type I and heterotic strings, and examines the symmetry structure in the D=3 case.

Findings

Open Type I F-branes unify Type I and heterotic strings.

F-theory exhibits U-duality symmetry with a unified gauge coset.

Parity projection simplifies the symmetry coset in D=3 case.

Abstract

We include in F-theory, through open Type I F-theory branes (F-branes), string theories with N = 1 supersymmetry, both Type I and heterotic. Type I branes are distinguished from Type II by worldvolume parity projection. The same open Type I branes describe both open Type I superstrings and closed heterotic upon different sectionings from F-branes to worldsheets, while closed Type I superstrings arise from closed Type I branes. (Type II superstrings come from closed Type II branes, as described previously.) F-theory manifests the exceptional-group U-duality symmetry, with all massless bosonic fields in a single gauge coset. This coset branches to the usual bosonic supergravity fields upon sectioning. We examine in detail the simple case of D = 3 F-theory: Parity projection reduces the Type II coset SL(5)/SO(3,2) to the Type I coset SO(3,3)/SO(2,1)2 = SL(4)/SO(2,2).