Anomaly Inflow of Rarita-Schwinger Field in 3 Dimensions

TL;DR

This paper investigates the anomaly inflow of the Rarita-Schwinger field in 3D, revealing spectral flow properties and confirming the absence of certain global anomalies, with implications for topological phases.

Contribution

It demonstrates the spectral flow of the Rarita-Schwinger operator is equivalent to that of the spin-3/2 Dirac operator and confirms anomaly inflow captures the global anomalies in 3D.

Findings

Spectral flow of Rarita-Schwinger operator equals that of spin-3/2 Dirac operator

No global anomalies of gauge-diffeomorphism transformations on spin manifolds

Anomalous phase on unorientable Pin+ manifolds is exp(3iπ/8)

Abstract

We study the anomaly inflow of the Rarita-Schwinger field with gauge symmetry in $3$ dimensions. We find that global anomalies of the Rarita-Schwinger field are obtained by the spectral flow, which is similar to Witten's $SU(2)$ global anomaly for a Weyl fermion. The Rarita-Schwinger operator is shown to be a self-adjoint Fredholm operator, and its spectral flow is determined by a path on the set of self-adjoint Fredholm operators with the gap topology. From the spectral equivalence of the spectral flow, we find that the spectral flow of the Rarita-Schwinger operator is equivalent to that of the spin-$3/2$ Dirac operator. From this fact, we confirm that the anomaly of the $3$-dimensional Rarita-Schwinger field is captured by the anomaly inflow. Finally, we find that there are no global anomalies of gauge-diffeomorphism transformations on spin manifolds with any gauge group. We also confirm that the anomalous phase of the partition function which corresponds to the generator of $\Omega_4^{{\rm Pin}^+}(pt)=\mathbb{Z}_{16}$ is $\exp(3i\pi /8)$ for the Rarita-Schwinger theory on unorientable ${\rm Pin}^+$ manifolds without gauge symmetry.