N=2 String Loops and Spectral Flow

TL;DR

This paper explores the role of spectral flow and hidden symmetries in N=2 string theory, constructing the loop measure and analyzing amplitude properties on flat backgrounds.

Contribution

It explicitly constructs the loop measure for N=2 strings and reveals the significance of spectral flow and hidden N=4 superconformal symmetry at arbitrary genus.

Findings

Spectral flow is crucial for understanding N=2 string amplitudes.

The hidden N=4 superconformal symmetry is non-linearly realized.

The paper discusses symmetry properties of N=2 string amplitudes on flat backgrounds.

Abstract

Based on our previous studies of the BRST cohomology of the critical N=2 strings, we construct the loop measure and make explicit the role of the spectral flow at arbitrary genus and Chern class, in a holomorphic field basis. The spectral flow operator attributes to the existence of the hidden `small' N=4 superconformal symmetry which is non-linearly realized. We also discuss the symmetry properties of N=2 string amplitudes on locally-flat backgrounds.