Extremal Correlators and Hurwitz Numbers in Symmetric Product Orbifolds

Understand

We study correlation functions of single-cycle chiral operators in the symmetric product orbifold of N supersymmetric four-tori.

• Correlators of twist operators are evaluated on covering surfaces, generally of different genera, where fields are single-valued.
• We compute some simple four-point functions and study how the sum over inequivalent branched covering maps splits under OPEs.
• We then discuss extremal n-point correlators, i.e.