Massive Spin 3/2 Electrodynamics

TL;DR

This paper investigates the properties, unitarity, and causality of a non-minimally coupled massive spin 3/2 model, exploring its phenomenological implications and higher spin generalizations, revealing persistent acausality issues.

Contribution

It provides a detailed analysis of the unitarity, causality, and degrees of freedom of the spin 3/2 model, including its relation to physical parameters and higher spin extensions.

Findings

The model's parameters relate to physical characteristics via low energy theorems.

None of the models studied, including truncated supergravity, are free of acausality.

The analysis covers both low and high energy regimes for unitarity and causality.

Abstract

We study the general non-minimally coupled charged massive spin 3/2 model both for its low energy phenomenological properties and for its unitarity, causality and degrees of freedom behaviour. When the model is viewed as an effective theory, its parameters (after ensuring the correct excitation count) are related to physical characteristics, such as the magnetic moment g factor, by means of low energy theorems. We also provide the corresponding higher spin generalisation. Separately, we consider both low and high energy unitarity, as well as the causality aspects of our models. None (including truncated N=2 supergravity) is free of the minimal model's acausality.