On the $\uptheta$-vacua and CP violation

Fuente: arXiv
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Autor principal: Kobakhidze, Archil
Formato: Preprint
Publicado: 2026
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author Kobakhidze, Archil
author_facet Kobakhidze, Archil
contents Recent claims have suggested the absence of CP violation in theories with a $θ$-vacuum structure, particularly in quantum chromodynamics. We highlight several key points, from a perspective that is not widely discussed in the literature, which clarify why such conclusions are incorrect. In particular, an open boundary in a finite-volume theory must be accompanied by boundary degrees of freedom, the edge modes, in order to preserve large gauge invariance and faithfully capture the topological features of the theory. In the infinite-volume limit, these edge states become non-dynamical, leaving the standard $\uptheta$-vacuum structure intact, irrespective of whether this limit is taken before or after summing over topological sectors. Consequently, the $\uptheta$-vacuum structure does give rise to observable CP violation once the theory is consistently quantised.
format Preprint
id arxiv_https___arxiv_org_abs_2604_02698
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On the $\uptheta$-vacua and CP violation
Kobakhidze, Archil
High Energy Physics - Theory
Recent claims have suggested the absence of CP violation in theories with a $θ$-vacuum structure, particularly in quantum chromodynamics. We highlight several key points, from a perspective that is not widely discussed in the literature, which clarify why such conclusions are incorrect. In particular, an open boundary in a finite-volume theory must be accompanied by boundary degrees of freedom, the edge modes, in order to preserve large gauge invariance and faithfully capture the topological features of the theory. In the infinite-volume limit, these edge states become non-dynamical, leaving the standard $\uptheta$-vacuum structure intact, irrespective of whether this limit is taken before or after summing over topological sectors. Consequently, the $\uptheta$-vacuum structure does give rise to observable CP violation once the theory is consistently quantised.
title On the $\uptheta$-vacua and CP violation
topic High Energy Physics - Theory
url https://arxiv.org/abs/2604.02698