Modifying topological sectors of gauge theories and applications

Novičić, Dušan (2026): Modifying topological sectors of gauge theories and applications. Dissertation, LMU München: Faculty of Physics

Abstract

The topological structure of gauge field configurations encodes essential global information about quantum field theories, including generalized global symmetries, conserved charges, and potential quantum anomalies. Such global data are not captured by local descriptions alone and can distinguish quantum theories with identical local operator content. In this thesis, we investigate how modifications of the topological sectors of gauge theories influence their global properties and physical consequences. We first discuss a general framework for modifying the global structure of Abelian higher-form gauge theories by constraining their characteristic classes, which encode topological charges and global data of the theory. These modifications are implemented directly at the level of the classifying space of the gauge theory using homotopy fiber construction. This provides a systematic method for constructing and studying new global variants of gauge theories while preserving their local field content. We show that such modifications can alter the spectrum of topological sectors and lead to additional global charges and anomaly structures. We then study the implications of nontrivial global gauge structures in extensions of the Standard Model with a non-Abelian dark sector. In particular, we consider theories in which the Standard Model and dark sector gauge groups are topologically linked through the gauging of a common subgroup of their center one-form symmetries. The resulting global structure modifies the allowed topological sectors and the quantization conditions of axion couplings. This leads to modified constraints on axion–photon interactions and, in certain cases, a significant reduction of the lower bound on the coupling, opening new phenomenological possibilities. We also analyze the consequences of these global modifications for matter representations, generalized symmetries, and topological defects.

• Item Type: Theses (Dissertation, LMU Munich)
• Keywords: Gauge theories, Topological properties, Generalized symmetries and anomalies, Axions
• Subjects: 500 Natural sciences and mathematics; 500 Natural sciences and mathematics > 530 Physics
• Faculties: Faculty of Physics
• Language: English
• Date of oral examination: 24. July 2026
• 1. Referee: Lüst, Dieter
• Signature of the printed copy: 0001/UMC 32139