Helicity-1/2 Mode as a Probe of Interactions of Massive Rarita-Schwinger Field

TL;DR

This paper investigates the interactions of a massive Rarita-Schwinger field, revealing that the helicity-1/2 mode signals the strong coupling scale and pathologies, providing insights into consistent theories like supergravity.

Contribution

It analyzes the helicity-1/2 mode in massive Rarita-Schwinger fields, establishing its role in identifying interaction consistency and UV cutoff bounds.

Findings

Helicity-1/2 mode signals the strong coupling scale.

Inconsistent interactions involve pathologies detectable via this mode.

Consistent models propagate the mode within the light cone.

Abstract

We consider the electromagnetic and gravitational interactions of a massive Rarita-Schwinger field. Stueckelberg analysis of the system, when coupled to electromagnetism in flat space or to gravity, reveals in either case that the effective field theory has a model-independent upper bound on its UV cutoff, which is finite but parametrically larger than the particle's mass. It is the helicity-1/2 mode that becomes strongly coupled at the cutoff scale. If the interactions are inconsistent, the same mode becomes a telltale sign of pathologies. Alternatively, consistent interactions are those that propagate this mode within the light cone. Studying its dynamics not only sheds light on the Velo-Zwanziger acausality, but also elucidates why supergravity and other known consistent models are pathology-free.