Transitions of orbifold vacua

Abstract

We study the global structure of vacua of heterotic strings compactified on orbifolds T 4 /Z N (N = 2, 3) in the presence of heterotic 5-branes. Gauge symmetry breaking associated with orbifold is described by instantons in the field theory. Phase transition between small instantons and heterotic 5-branes provides top-down, stringy account to the spectrum and modular invariance condition. Also it takes us from one vacuum to another by emitting and absorbing instantons. This means that many vacua with different gauge theory are in fact connected and are inherited from perturbative vacua. It follows that there are also transitions among twisted fields, heterotic 5-branes and instantons. *

Non-perturbative heterotic duals of M-theory on G2 orbifolds

“…The right-hand side of the anomaly cancellation condition may be modified non-perturbatively by the presence of background NS5-branes. We work in a limit where any wrapped NS5-branes are represented by point-like instantons [43], so that both perturbative and non-perturbative contributions are contained in the trF ∧ F term.…”

Small-Instanton Transitions in F-theory

“…Increasingly many phenomena have been unified under such dualities. For instance, recently it has been understood that twisted strings localized on orbifolds can take part in the transition [14].…”