On the $i\phi^{3}$ $\mathcal{PT}$-symmetric Scalar Field Theory

TL;DR

This paper investigates the $i\phi^{3}$ scalar field theory, revealing it is fundamentally Hermitian with ghost states and instability issues, and challenges previous non-Hermitian interpretations by analyzing its solutions and transformations.

Contribution

It demonstrates that the $i\phi^{3}$ theory is Hermitian with ghost states, and shows that previous non-Hermitian approaches are invalid, providing new insights into its solitonic solutions.

Findings

The field is a pure imaginary solitary wave.

The theory suffers from ghost states and instability.

Previous non-Hermitian treatments are invalid.

Abstract

In this work, we show that, for the $i\phi^{3}$ scalar field theory, their exists a contradiction between the assumption that the field is real and the fact that the quantized as well as the classical fields have to satisfy the Klein-Gordon equation. In solving the Klein-Gordon equation for the theory under investigation, we realized that the field is a pure imaginary solitary wave which spoils out the non-Hermiticity of the theory. Thus, instead of being non-Hermitian, the $i\phi^{3}$ scalar field theory is a kind of a Hermitian-Lee-Wick theory which suffers from the existence of the famous ghost states and instability problems. We applied a Canonical transformation to obtain a Non-Hermitian and non-$\mathcal{PT}$-symmetric representation which leads to the invalidity of the previous trials in the literature to cure the ghost states problem. Moreover, the solitonic solution is a non-topological one which is a very strange result to appear for a one component field theory. To account for this strange result, we conjecture that the $i\phi^{3}$ scalar field theory has an equivalent Hermitian and non-Lee wick theory that have a conserved Noether current.