Revisiting the Okubo-Marshak argument

TL;DR

This paper reevaluates the Okubo-Marshak argument using modern quantum field theory tools, questioning the assumption of a strong CP problem in QCD and emphasizing the role of local symmetry and gauge invariance.

Contribution

It applies modular localization and string-localized fields to critically analyze the strong CP problem in QCD, challenging previous assumptions.

Findings

Local symmetry emerges from quantum theory without assuming global gauge invariance.

The strong CP problem may not be a fundamental issue in QCD.

Modern tools provide new insights into gauge invariance and symmetry in quantum field theory.

Abstract

Modular localization and the theory of string-localized fields have revolutionized several key aspects of quantum field theory. They reinforce the contention that local symmetry emerges directly from quantum theory, but global gauge invariance remains in general an unwarranted assumption, to be examined case by case. Armed with those modern tools, we reconsider here the classical Okubo-Marshak argument on the non-existence of a "strong CP problem" in quantum chromodynamics.