Two-point String Amplitudes Revisited by Operator Formalism

TL;DR

This paper revisits two-point string amplitudes using the operator formalism, demonstrating that non-zero amplitudes can arise from a BRST exact operator, challenging the traditional view of their vanishing.

Contribution

It introduces a BRST exact operator in the operator formalism that produces non-zero two-point string amplitudes, providing a new perspective on their calculation.

Findings

Two-point amplitudes can be non-zero due to BRST exact operators.

Revisiting the amplitude calculation clarifies the role of residual gauge symmetry.

The operator formalism offers a consistent framework for these amplitudes.

Abstract

So far we have considered that a two-point string amplitude vanishes due to the infinite volume of residual gauge symmetry. However recently Erbin-Maldacena-Skliros have suggested that the two-point amplitude can have non-zero value, because one can cancel the infinite volume by the infinity coming from on-shell energy conservation. They derived the two-point function by Fadeev-Popov method. In this paper we revisit this two-point string amplitude in the operator formalism. We find the mostly BRST exact operator which yields non-zero two-point amplitudes.