Probing the unitarity of the renormalizable theory of massive conformal gravity

TL;DR

This paper investigates the unitarity of massive conformal gravity, demonstrating that the gauge dependence of complex poles associated with ghost states implies the theory remains unitary.

Contribution

It reveals that the gauge dependence of complex poles in the theory's energy plane ensures the unitarity of the renormalizable massive conformal gravity.

Findings

Complex poles are gauge dependent.

Gauge dependence implies unitarity.

Ghost states do not violate unitarity.

Abstract

The presence of an unstable massive spin-2 ghost state in the renormalizable theory of massive conformal gravity leads to a pair of complex poles appearing in the first sheet of the energy plane. Here we show that the positions of these poles are gauge dependent, which makes the theory unitary.