On off-shell bosonic string amplitudes

TL;DR

This paper presents a straightforward method for calculating off-shell one-loop amplitudes in bosonic string theory involving any number of massless particles, highlighting their properties such as transversality.

Contribution

It introduces a simple prescription for off-shell one-loop amplitude computations in bosonic string theory, applicable to both open and closed strings, with analysis of their properties.

Findings

Off-shell one-loop amplitudes can be computed systematically.

Two-string one-loop amplitudes are shown to be transverse.

The method applies to any number of external massless particles.

Abstract

We give a simple prescription for computing, in the framework of the bosonic string theory, off-shell one-loop amplitudes with any number of external massless particles, both for the open and for the closed string. We discuss their properties and, in particular, for the two-string one-loop amplitudes we show their being transverse.