New Phases of String Theory and 6d RG Fixed Points via Branes at Orbifold Singularities

TL;DR

This paper explores new six-dimensional phases of string theory involving branes at orbifold singularities, revealing theories with extra tensor multiplets and infinite classes of RG fixed points.

Contribution

It introduces novel phases of string theories with extra tensor multiplets arising from small instantons on orbifold singularities, constructed via orientifolds.

Findings

Existence of new 6d string theory phases with extra tensor multiplets

Construction of these theories via orientifold techniques

Identification of infinite classes of 6d RG fixed point theories

Abstract

We discuss type II and type I branes at general ADE type orbifold singularities. We show that there are new phases of type I or heterotic string theory in six dimensions, involving extra tensor multiplets, which arise when small instantons sit on orbifold singularities. The theories with extra tensor multiplets are explicitly constructed via orientifolds. The world-volume theories in type IIB or type I five-branes at orbifold singularities lead to the existence of several infinite classes of six dimensional, interacting, renormalization group fixed point theories.