Non-invertible SPTs: an on-site realization of (1+1)d anomaly-free fusion category symmetry

Non-invertible SPTs: an on-site realization of (1+1)d anomaly-free fusion category symmetry

🎙 Xinping Yang 👥 2K 📅 December 3, 2025 ⏱ 64 min 👁 136 📄 original study 🧭 2026-08-15
Available in: English (current) Français

Keywords

non-invertible symmetrySPTfusion categorylattice modeltopological order

Summary

Xinping Yang presents a microscopic lattice realization of non-invertible symmetry-protected topological (SPT) phases in (1+1) dimensions. The talk focuses on gapped quantum phases described by TQFTs, with symmetries represented by topological defect lines forming a fusion category. The speaker emphasizes the need to generalize the notion of on-site symmetry for non-invertible operators, which typically act non-locally. Using the Tanaka duality and coend construction, she obtains a Hopf algebra that encodes the symmetry action. She then constructs matrix product operators (MPOs) that realize the symmetry on the lattice, with a generalized on-site condition requiring the virtual bond dimension to match the quantum dimension of simple objects. The talk provides an alternative classification of SPT phases via matrix algebras, and discusses challenges such as the lack of stacking structure for non-invertible symmetries. An example of the Rep(D8) symmetry is used to illustrate the construction, and the speaker shows how to build commuting projector Hamiltonians using Q-systems. The talk concludes with a discussion of edge modes and the permutation of SPT phases.

169 words

Critical Evaluation

Value of the Information & Strength of the Argument

The talk provides a novel and rigorous framework for realizing non-invertible symmetries on the lattice, which is a significant contribution to the field. The argumentation is well-structured, building from categorical foundations to explicit lattice models. The speaker carefully explains the mathematical tools and their physical relevance, making a compelling case for the generalized on-site condition. The use of the Rep(D8) example helps illustrate the abstract concepts, and the discussion of limitations (e.g., lack of stacking) shows critical thinking. However, the presentation is highly technical and may be challenging for non-specialists, and the lack of published results limits immediate verification.

Scientific Rigor, Source Quality, Title Accuracy

The talk demonstrates strong scientific rigor, with clear definitions and logical progression. The speaker references prior work (e.g., by Sahan and Shuhan) and builds on established categorical frameworks. The title accurately reflects the content, which focuses on on-site realization of non-invertible SPTs. The sources cited are primarily from the description, including the seminar page and institutional links, but no specific papers are mentioned in the talk. The absence of explicit citations in the presentation is a minor weakness, but the mathematical formalism is self-contained.

198 words

Title / Content Match

The title accurately reflects the content, which focuses on constructing non-invertible SPTs with on-site symmetry.

Quality & Reliability

8/10

The talk presents original research with rigorous mathematical formalism, but lacks peer-reviewed publication details and is a seminar presentation.

Key Moments

Cited Sources

Concurring Sources

  • Seminar page — Official event page, consistent with the talk's content.

Contribution & Novelties

The talk presents a novel lattice realization of non-invertible SPTs with a generalized on-site condition, providing a concrete construction beyond existing work. It offers an alternative classification via matrix algebras and addresses the absence of stacking structure. The use of Q-systems for commuting projectors is a fresh perspective.

Pour aller plus loin :

  • Fusion category — Background on the categorical framework.
  • Matrix product operator — Relevant to the MPO construction.
  • Hopf algebra — Mathematical structure used for symmetry action.

79 words

Radar Profile

The radar profile shows high scores in technical level and information quality, indicating a rigorous and dense presentation. The moderate score in fiabilite_globale reflects the lack of published sources, while the balanced scores suggest a well-rounded talk.

Reliability 8/10