Testing symmetries in effective models of higher derivative field theories

TL;DR

This paper develops a perturbative approach to higher derivative field theories that preserves Lorentz invariance and recovers certain discrete symmetries in the low-energy effective models, addressing stability issues.

Contribution

It introduces a perturbative formulation for higher derivative theories that yields stable, symmetry-preserving low-energy effective models, exemplified by the Maxwell-Chern-Simons theory.

Findings

Recovery of discrete symmetries in the effective theory

Positive-definite Hamiltonian in the low-energy limit

Lorentz invariance preserved in the effective model

Abstract

Higher derivative field theories with interactions raise serious doubts about their validity due to severe energy instabilities. In many cases the implementation of a direct perturbation treatment to excise the dangerous negative-energies from a higher derivative field theory may lead to violations of Lorentz and other symmetries. In this work we study a perturbative formulation for higher derivative field theories that allows the construction of a low-energy effective field theory being a genuine perturbations over the ordinary-derivative theory and having a positive-defined Hamiltonian. We show that some discrete symmetries are recovered in the low-energy effective theory when the perturbative method to reduce the negative-energy degrees of freedom from the higher derivative theory is applied. In particular, we focus on the higher derivative Maxwell-Chern-Simons model which is a Lorentz invariant and parity-odd theory in 2+1 dimensions. The parity violation arises in the effective action of QED$_3$ as a quantum correction from the massive fermionic sector. We obtain the effective field theory which remains Lorentz invariant, but parity invariant to the order considered in the perturbative expansion.