On the BRST Cohomology of N=2 Strings

TL;DR

This paper investigates the BRST cohomology of critical N=2 NSR strings, employing chiral bosonization to clarify picture-changing and spectral flow, and computes the string measure incorporating ghost number-changing insertions for various amplitudes.

Contribution

It provides an explicit analysis of picture-changing and spectral flow in N=2 strings using holomorphic fields, and derives the string measure with ghost insertions at arbitrary genus and instanton number.

Findings

Explicit formulation of picture-changing and spectral flow in a holomorphic basis

Derivation of the string measure with ghost insertions for arbitrary genus

Analysis of BRST cohomology in N=2 NSR strings

Abstract

We analyze the BRST cohomology of the critical N=2 NSR string using chiral bosonization. Picture-changing and spectral flow is made explicit in a holomorphic field basis. The integration of fermionic and U(1) moduli is performed and yields picture- and U(1) ghost number-changing insertions into the string measure for n-point amplitudes at arbitrary genus and U(1) instanton number.