Old and New No Go Theorems on Interacting Massless Particles in Flat Space

TL;DR

This paper reviews fundamental no-go theorems limiting the spin of massless particles interacting with gravity in flat space, discusses recent extensions, and resolves apparent counterexamples to these theorems.

Contribution

It consolidates and discusses model-independent no-go theorems on massless particle interactions, including recent extensions and their implications.

Findings

Massless particles interacting with gravity in Minkowski space can have at most spin two.

The paper clarifies and resolves a puzzle related to a potential counterexample.

It emphasizes the robustness of no-go theorems in constraining particle interactions.

Abstract

We review model independent arguments showing that massless particles interacting with gravity in a Minkowski background space can have at most spin two. These arguments include a classic theorem due to Weinberg, as well as a more recent extension of the Weinberg-Witten theorem. A puzzle arising from an apparent counterexample to these theorems is examined and resolved.