E8 × E8 small instantons in matrix theory

Small E8 Instantons and Tensionless Non Critical Strings

T-duality is used to extract information on an instanton of zero size in the E8 ×E8 heterotic string. We discuss the possibility of the appearance of a tensionless antiself-dual non-critical string through an implementation of the mechanism suggested by Strominger of two coincident 5-branes. It is argued that when an instanton shrinks to zero size a tensionless non-critical string appears at th...

Small Instantons in Matrix Theory

F-Theory Duals of Nonperturbative Heterotic E8 × E8 Vacua in Six Dimensions

We present a systematic way of generating F-theory models dual to nonperturbative vacua (i.e., vacua with extra tensor multiplets) of heterotic E8×E8 strings compactified on K3, using hypersurfaces in toric varieties. In all cases, the Calabi-Yau is an elliptic fibration over a blow up of the Hirzebruch surface IFn. We find that in most cases the fan of the base of the elliptic fibration is vis...

Regular Two-graphs from the Even Unimodular Lattice E8 + E8

This is a revised version of the rst part of 8]. Each two-graph is in one-to-one correspondence with a set of equiangular lines. This implies that a two-graph is represented by a system of vectors of equal odd norm with mutual inner products

A Standard Model from the E8 × E8 Heterotic Superstring

In a previous paper, we introduced a heterotic standard model and discussed its basic properties. This vacuum has the spectrum of the MSSM with one additional pair of Higgs-Higgs conjugate fields and a small number of uncharged moduli. In this paper, the requisite vector bundles are formulated; specifically, stable, holomorphic bundles with structure group SU(N) on smooth Calabi-Yau threefolds ...