Massive Higher Spin States in String Theory and the Principle of Equivalence

TL;DR

This paper investigates the gravitational interactions of massive higher spin states in string theory, revealing that consistent interactions depend on a parameter h that differs from field theory predictions due to the influence of a tower of massive states.

Contribution

It introduces a gravitational quadrupole h-factor for massive string states and demonstrates how string interactions differ from field theory due to the tower of massive states.

Findings

Non-minimal interactions parametrized by h≠1

String interactions involve a tower of massive states

Differences from field theory due to complete string spectrum

Abstract

In this paper we study three point functions of the Type II superstring involving one graviton and two massive states, focusing in particular on the spin-7/2 fermions at the first mass level. Defining a gravitational quadrupole ``h-factor'', we find that the non-minimal interactions of string states in general are parametrized by $h\ne1$, in contrast to the preferred field theory value of h=1 (for tree-level unitarity). This difference arises from the fact that consistent gravitational interactions of strings are related to the presence of a complete tower of massive states, not present in the ordinary field theory case.