Dr. Atsushi Ueda | Monopole scattering on the lattice

Dr. Atsushi Ueda | Monopole scattering on the lattice

Title history
  • Dr. Atsushi Ueda | Monopole scattering on the lattice — observed on 20261103-0944 UTC (YouTube)

by Atsushi Ueda · View the channel on PSI

Formal & Physical Sciences Physics PHPhysicsPHPParticle and high-energy physics
🎙 Atsushi Ueda 👥 8K 📅 November 2, 2026 ⏱ 46 min 👁 111 📄 original study 🧭 2026-11-03
Available in: English (current) Français

Keywords

monopolelatticeduality defecttensor networkCallan-Rubakov

Summary

The seminar, given by Dr. Atsushi Ueda at the Isaac Newton Institute, addresses the monopole scattering paradox in quantum field theory, where the S-matrix appears non-unitary in the one-particle sector. The speaker first reviews the original Callan-Rubakov paradox, which states that a chiral fermion scattered by a magnetic monopole does not return as a simple electron, but rather as a non-local object with a topological string. He then introduces a lattice model that realizes this phenomenon microscopically. The model couples two Ising chains with different phases (symmetric and spontaneously broken) via a defect, and numerical simulations show perfect transmission at a special ‘duality’ point where the two sides have identical spectra. The key mechanism is the construction of a duality defect, implemented through a tensor network unitary transformation that promotes virtual indices to physical ones. This construction generalizes to other models, such as the Haldane chain and 2D systems, where the outgoing excitation becomes a string-like object detected by non-local operators. Finally, the speaker demonstrates that folding the model yields a boundary with a decoupled Majorana mode, providing a microscopic explanation for the boundary entropy and the unitarity restoration. The talk offers a universal lattice understanding of an old paradox, avoiding the need for conformal field theory or integrability.

209 words

Critical Evaluation

Value of the Information & Strength of the Argument

The value of this presentation lies in its novel approach to resolving a long-standing paradox in quantum field theory using explicit lattice constructions. The speaker provides a clear logical progression from the paradox to a concrete solvable model, supported by numerical simulations and tensor network arguments. The argumentation is robust: the model is simple enough to be exactly solvable in certain limits, yet captures the essential physics of the Callan-Rubakov effect. The use of duality and unitary transformations is well-motivated and elegantly connects to existing concepts like boundary conformal field theory. The numerical evidence for perfect transmission and the emergence of string order parameters strengthens the claims. However, the presentation assumes a high level of familiarity with quantum field theory, tensor networks, and duality, so the argumentation is not accessible to a general audience, but for a specialist it is compelling and well-structured.

Scientific Rigor, Source Quality, Title Accuracy

The scientific rigor is high: the talk is presented at a leading mathematical sciences institute, and the speaker cites relevant literature (Callan-Rubakov, Affleck-Ludwig, etc.) and discusses recent solutions from 2023-2024. The title accurately reflects the content, as the focus is on monopole scattering realized on a lattice. The sources cited include the Isaac Newton Institute’s website and the specific seminar page, which provide context and additional resources, but the talk itself does not provide direct citations or references to specific papers beyond the collaborators. The lack of detailed reference lists in the talk is mitigated by the existence of the seminar page with likely further information. The presentation is methodologically sound, with clear definitions and numerical experiments.

275 words

Title / Content Match

The title accurately reflects the content: the speaker presents a lattice model for monopole scattering, addressing the Callan-Rubakov paradox.

Quality & Reliability

9/10

The talk is a rigorous research presentation at the Isaac Newton Institute, with a clear logical structure, numerical evidence, and careful theoretical reasoning. The speaker is an established researcher and the results are presented with precision.

Key Moments

Markers derived by PSI from the transcript: the creator did not define chapters.

Cited Sources

Concurring Sources

Contribution & Novelties

The talk presents a novel lattice realization of the Callan-Rubakov monopole scattering, demonstrating that the paradox can be resolved by including dynamical boundary degrees of freedom. The key innovation is the use of a duality defect constructed via tensor networks, which enables perfect transmission and the emergence of topological string operators. This approach provides a universal, non-perturbative framework that does not rely on integrability or conformal field theory, making the physics accessible to a broad range of lattice models. The microscopic explanation in terms of a decoupled Majorana mode offers new insight into the boundary entropy and the mechanism of unitarity restoration.

Pour aller plus loin :

  • Callan-Rubakov effect — The original effect described, relevant to the paradox discussed.
  • Tensor network — The mathematical tool used in the construction of duality defects and matrix product states.
  • Duality (physics) — The concept of duality central to the talk, including Kramers-Wannier duality.
  • Majorana fermion — The relativistic fermion that appears as a zero mode in the folded model.

166 words

Radar Profile

The radar profile shows a highly technical and rigorous talk, with maximum scores in technical level and high scores in information quality and reliability, but slightly lower in quantity of information due to the concise 46-minute format. This indicates a dense, specialized presentation aimed at experts.

Reliability 9/10