Elusive Worldsheet Instantons in Heterotic String Compactifications

Understand

We compute the spectrum of massless gauge singlets in some heterotic string compactifications using Landau-Ginzburg, orbifold and non-linear sigma-model methods.

• This probes the worldsheet instanton corrections to the quadratic terms in the spacetime superpotential.
• Previous results predict that some of these states remain massless when instanton effects are included.
• We find vanishing masses in many cases not covered by these predictions.