Scattering Amplitudes and the CPT theorem in String Theory

TL;DR

This paper explores the role of CPT symmetry in first-quantized string theories, demonstrating that the CPT theorem holds in all such theories within even-dimensional Minkowski backgrounds.

Contribution

It provides a proof that the CPT theorem is valid for all first-quantized perturbative string theories in even-dimensional Minkowski space.

Findings

CPT symmetry is confirmed in all first-quantized string theories.

The CPT theorem applies in Minkowski backgrounds of even dimension greater than 2.

The paper clarifies the role of CPT in world-sheet and space-time formulations.

Abstract

We discuss the role of the CPT transformation in first quantized string theories, both on the world-sheet and in the space-time. We explicitly show that the space-time CPT theorem holds for all first-quantized (perturbative) string theories in a Minkowski background of even dimension $D>2$.