Discrete spacetime symmetries and particle mixing in non-Hermitian scalar quantum field theories

• URL: http://arxiv.org/abs/2006.06656v3
• Date: Mon, 4 Jan 2021 18:08:47 GMT
• Title: Discrete spacetime symmetries and particle mixing in non-Hermitian scalar quantum field theories
• Authors: Jean Alexandre, John Ellis, Peter Millington
• Abstract summary: We discuss second quantization, discrete symmetry transformations and inner products in free non-Hermitian quantum field theories with PT symmetry. We focus on a prototype model of two complex scalar fields with anti-Hermitian mass mixing.
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• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: We discuss second quantization, discrete symmetry transformations and inner products in free non-Hermitian scalar quantum field theories with PT symmetry, focusing on a prototype model of two complex scalar fields with anti-Hermitian mass mixing. Whereas the definition of the inner product is unique for theories described by Hermitian Hamiltonians, its formulation is not unique for non-Hermitian Hamiltonians. Energy eigenstates are not orthogonal with respect to the conventional Dirac inner product, so we must consider additional discrete transformations to define a positive-definite norm. We clarify the relationship between canonical-conjugate operators and introduce the additional discrete symmetry C', previously introduced for quantum-mechanical systems, and show that the C'PT inner product does yield a positive-definite norm, and hence is appropriate for defining the Fock space in non-Hermitian models with PT symmetry in terms of energy eigenstates. We also discuss similarity transformations between PT-symmetric non-Hermitian scalar quantum field theories and Hermitian theories, showing that they would require modification in the presence of interactions. As an illustration of our discussion, we compare particle mixing in a Hermitian theory and in the corresponding non-Hermitian model with PT symmetry, showing how the latter maintains unitarity and exhibits mixing between scalar and pseudoscalar bosons.

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