researchseminars.org

Jesse Woods (University of Bern)
2025-09-19 07:00 - 08:00 UTC | https://researchseminars.org/talk/EUPAC-TP/3/
Title: Defining QFT Categorically I (https://researchseminars.org/talk/EUPAC-TP/3/)
by Jesse Woods (University of Bern) as part of Europe and Pacific Theoretical Physics

Abstract
In preparation to study Generalised (Categorical) Symmetries, we provide motivation and give an introduction to some very basic, but relevant, concepts in Category Theory. We will introduce monoidal categories before showing that the expected properties of Topological Quantum Field Theory follow naturally from a categorical definition. We compute some basic results of TQFT to demonstrate the utility of categories in physics.

Jonathan Skelton (University of Sydney)
2025-09-26 07:00 - 08:00 | https://researchseminars.org/talk/EUPAC-TP/5/
Title: Symmetries as Topological Operators (https://researchseminars.org/talk/EUPAC-TP/5/)
by Jonathan Skelton (University of Sydney) as part of Europe and Pacific Theoretical Physics

Abstract
In this talk I'll discuss extended symmetry defect operators and how they naturally arise from symmetries in the quantum theory.

The focus will be on ordinary symmetries; these are referred to as 0-form topological group-like symmetries in the modern literature. First I will discuss classical symmetries of Lagrangian field theory. In the second part I will discuss their analogues in the quantised theory, and outline and a sketch a proof of their properties.

Joey Faller (University of Queensland)
2025-10-03 07:00 - 08:00 | https://researchseminars.org/talk/EUPAC-TP/6/
Title: One-Form Symmetries and Confinement (https://researchseminars.org/talk/EUPAC-TP/6/)
by Joey Faller (University of Queensland) as part of Europe and Pacific Theoretical Physics

Abstract
Global symmetries, traditionally understood to act on local operators, are a cornerstone of QFT. This talk provides a pedagogical introduction to their generalisation: higher-form symmetries; these act on non-local, extended operators like Wilson lines. We will begin by showing how the concept of a conserved charge can be extended from 0-form to 1-form symmetries and demonstrate that this framework is consistent with Noether's theorem.

In a gauge theory, two principal types of 1-form symmetries can emerge: a 'magnetic' symmetry of topological origin from the Bianchi identity ($dF=0$), and an 'electric' symmetry arising from the dynamical equations of motion. It is this electric 1-form symmetry that provides a novel method to analyse confinement.
The primary application of this framework is to show how the status of this 1-form symmetry, whether it is spontaneously broken or preserved, precisely determines whether confinement is present or not.

Adèle Le Borgne (University of Bern)
2025-10-10 07:00 - 08:00 | https://researchseminars.org/talk/EUPAC-TP/7/
Title: Landau-Ginzburg theory for 1-form symmetries (https://researchseminars.org/talk/EUPAC-TP/7/)
by Adèle Le Borgne (University of Bern) as part of Europe and Pacific Theoretical Physics

Abstract
To conclude the first block of seminars on higher form symmetry, I will review the first four sections of $\textbf{Mean string field theory: Landau-Ginzburg theory for 1-form symmetries}$ by Nabil Iqbal, John McGreevy.

$\textit{Abstract of the paper:}$

By analogy with the Landau-Ginzburg theory of ordinary zero-form symmetries, we introduce and develop a Landau-Ginzburg theory of one-form global symmetries, which we call mean string field theory. The basic dynamical variable is a string field – defined on the space of closed loops – that can be used to describe the creation, annihilation, and condensation of effective strings. Like its zero-form cousin, the mean string field theory provides a useful picture of the phase diagram of broken and unbroken phases. We provide a transparent derivation of the area law for charged line operators in the unbroken phase and describe the dynamics of gapless Goldstone modes in the broken phase. The framework also provides a theory of topological defects of the broken phase and a description of the phase transition that should be valid above an upper critical dimension, which we discuss. We also discuss general consequences of emergent one-form symmetries at zero and finite temperature.

Jonathan Skelton
2025-10-17 07:00 - 08:00 | https://researchseminars.org/talk/EUPAC-TP/8/
Title: Non-invertible Chiral Symmetry and the ABJ Anomaly (https://researchseminars.org/talk/EUPAC-TP/8/)
by Jonathan Skelton as part of Europe and Pacific Theoretical Physics

Abstract
In this talk I will derive the chiral (ABJ) anomaly, and briefly outline its connection to non-invertible (generalised) symmetries.

Jesse Woods (University of Bern)
2025-10-24 07:00 - 08:00 | https://researchseminars.org/talk/EUPAC-TP/9/
Title: Degenerate Ground States (https://researchseminars.org/talk/EUPAC-TP/9/)
by Jesse Woods (University of Bern) as part of Europe and Pacific Theoretical Physics

Abstract
Despite their common occurrence in our studies, degenerate spectra are rare and special. In this talk, we will briefly sketch the argument of eigenvalue repulsion and explain why degenerate Hamiltonians are not the norm. We will also demonstrate how familiar mechanisms for degeneracy fail in Quantum Mechanics. Next, anomalies will be discussed as an invariant for diagnosing degeneracy. To conclude, we will discuss projective representations and how to realise anyon parastatics on the torus and the associated ground state degeneracy, to set the scene for future discussions on fusion, anomalies, and inflow.

Jesse Woods (University of Bern)
2025-10-31 08:00 - 09:00 | https://researchseminars.org/talk/EUPAC-TP/10/
Title: Anomalies and Inflow I (https://researchseminars.org/talk/EUPAC-TP/10/)
by Jesse Woods (University of Bern) as part of Europe and Pacific Theoretical Physics

Abstract
We introduce anomalies as non-trivial fusions of symmetry defects. We introduce the inflow mechanism and the mapping torus.

Jonathan Skelton
2025-11-07 08:00 - 09:30 | https://researchseminars.org/talk/EUPAC-TP/11/
Title: Anomalies and Inflow II (https://researchseminars.org/talk/EUPAC-TP/11/)
by Jonathan Skelton as part of Europe and Pacific Theoretical Physics

Abstract: TBA

Lukasz T. Stepien (University of the National Education Commission, Krakow)
2026-03-27 08:00 - 09:00 | https://researchseminars.org/talk/EUPAC-TP/17/
Title: Bogomolny equations for some field-theoretical models (https://researchseminars.org/talk/EUPAC-TP/17/)
by Lukasz T. Stepien (University of the National Education Commission, Krakow) as part of Europe and Pacific Theoretical Physics

Abstract
The Bogomolny equations, if they can be derived for a given field-theoretical model, give a valuable chance for seeking topologically stable soliton solutions for such model. I will present a method based on variational calculus, of deriving Bogomolny equations for some field-theoretical models, and certain solutions of these equations, too.

Bartosz Pyszkowski
2026-04-17 07:00 - 08:00 | https://researchseminars.org/talk/EUPAC-TP/20/
Title: An Introduction to Double String Theory and Non-Riemannian Backgrounds (https://researchseminars.org/talk/EUPAC-TP/20/)
by Bartosz Pyszkowski as part of Europe and Pacific Theoretical Physics

Abstract
This talk introduces Double Field Theory (DFT) in the context of string theory, with a focus on its application to "non-Riemannian" backgrounds following arXiv:2008.03084. As a case study, we consider a particular example in which the BRST cohomology simplifies, containing only states at the first excited level. We then briefly examine the consistency of the theory by analyzing the modular invariance of the one-loop torus partition function. To keep the discussion pedagogical, a brief review of BRST quantization and modular invariance in string theory will be provided. No prior familiarity with DFT is assumed, and all are welcome.

Adèle Le Borgne (University of Bern)
2026-05-15 07:00 - 08:00 | https://researchseminars.org/talk/EUPAC-TP/29/
Title: Trapping-potential dependence of the unitary Fermi gas at the BCS-BEC crossover (https://researchseminars.org/talk/EUPAC-TP/29/)
by Adèle Le Borgne (University of Bern) as part of Europe and Pacific Theoretical Physics

Abstract
Cold-atom experiments which measure Fermi-gas properties near unitarity confine fermionic atoms to a region of space using trapping potentials of various shapes. The presence of a trapping potential introduces a new characteristic physical scale in the superfluid EFT which, inter alia, describes the acoustic branch of excitations in the far infrared well below the scale of the superfluid gap. In this EFT there is a clear hierarchy of scales, and corrections to the homogeneous system due to the trapping potential may be organized into three regions with distinct power counting that relies on both the EFT derivative expansion, and the WKB approximation, which is an expansion in gradients of the trapping potential. The energy spectrum of the superfluid system is obtained in each of the regions by explicit computation of the phonon-field fluctuations, and by the modifications to the dynamic structure factor due to the corresponding density fluctuations. The most significant deviations from linear dispersion due to the trapping potential are found in the far infrared region of the superfluid EFT.

Jesse Woods (University of Bern)
2026-05-22 07:00 - 08:00 | https://researchseminars.org/talk/EUPAC-TP/30/
Title: Semiclassics at the Cusp (https://researchseminars.org/talk/EUPAC-TP/30/)
by Jesse Woods (University of Bern) as part of Europe and Pacific Theoretical Physics

Abstract
In gauge theory, physical observables are inherently non-local and notoriously subtle. Wilson loops play a central role in understanding non-perturbative phenomena spanning high-energy and condensed matter physics. We explore the recent results of arXiv:2604.15422. Using the semiclassical method of large charge, we analytically determine the anomalous scaling dimension of Wilson lines with cusps in the Abelian Higgs model to NNLO, resumming perturbation theory in the quartic coupling at each order. This quantity encodes rich physics: radiation from deflected particles, defect fusion, and the superconducting phase transition. Our results interpolate between perturbative and large-charge regimes, accessing domains that are invisible in fixed-order perturbation theory, bridging perturbative and non-perturbative physics in strongly coupled CFTs.

Alessandro Duci (Milan Bicocca U)
2026-06-05 07:00 - 08:00 | https://researchseminars.org/talk/EUPAC-TP/31/
Title: SymTFT in Superspace (https://researchseminars.org/talk/EUPAC-TP/31/)
by Alessandro Duci (Milan Bicocca U) as part of Europe and Pacific Theoretical Physics

Abstract
We propose a manifestly supersymmetric formulation of the Symmetry Topological Field Theory (SuSymTFT) for theories with supersymmetry. The SymTFT is a framework that helps organizing symmetries and anomalies of a QFT. Albeit a lot of activity in the field has been devoted to the construction of the SymTFT for the bosonic symmetry structure, the fermionic case has not been analyzed in detail. Here, we consider the most prominent example of theories exhibiting fermionic symmetries, that is supersymmetric models. These are most naturally formulated on supermanifolds, where the supergeometry approach allows for a manifest organization of the symmetries according to their fermionic grading. We provide the general construction of the SuSymTFT as a super-BF theory living in a (n|m)-dimensional supermanifold and check our proposal in two particular examples, the compact and the chiral super-bosons in two dimensions.

Zong-Zhe Du (University of Notthingham)
2026-05-29 07:00 - 08:00 | https://researchseminars.org/talk/EUPAC-TP/32/
by Zong-Zhe Du (University of Notthingham) as part of Europe and Pacific Theoretical Physics

Abstract: TBA
