Small Instanton Transitions in Heterotic M-Theory

TL;DR

This paper explores non-perturbative phase transitions in heterotic M-theory where five-branes contact boundary branes, transforming into small instantons and affecting gauge groups and matter content.

Contribution

It provides a detailed analysis of small instanton phase transitions, including conditions for their occurrence and explicit examples relevant to phenomenology.

Findings

Conditions for small instanton phase transitions are derived.

Explicit examples demonstrating phenomenological implications are presented.

Transitions can alter the number of families and gauge groups.

Abstract

We discuss non-perturbative phase transitions, within the context of heterotic M-theory, which occur when all, or part, of the wrapped five-branes in the five-dimensional bulk space come into direct contact with a boundary brane. These transitions involve the transformation of the five-brane into a ``small instanton'' on the Calabi-Yau space at the boundary brane, followed by the ``smoothing out'' of the small instanton into a holomorphic vector bundle. Small instanton phase transitions change the number of families, the gauge group or both on the boundary brane, depending upon whether a base component, fiber component or both components of the five-brane class are involved in the transition. We compute the conditions under which a small instanton phase transition can occur and present a number of explicit, phenomenologically relevant examples.