Pith. sign in

REVIEW 8 minor 16 cited by

Simons Lectures on Categorical Symmetries

T0 review · 0 major / 8 minor · reviewed 2026-08-12 · deepseek-v4-flash

Pith's one-line read This volume argues that every global symmetry of a quantum field theory is a topological defect operator, and that these defects assemble into a higher category that constrains the theory's dynamics.

desk verdict A solid, well-referenced set of lecture notes that gives newcomers a working tour of categorical symmetries; not a research paper, but it deserves serious review as a pedagogical volume. read the letter →

arxiv 2411.09082 v1 pith:GMEY4VCO submitted 2024-11-13 math-ph hep-thmath.ATmath.CTmath.MPmath.QA

classification math-phhep-thmath.ATmath.CTmath.MPmath.QA MSC 81T1381T4557R5618M15
keywords categoricalsymmetriestopologicaldefectshighercategoriesquantumfieldtheoryanomaliesnon-invertiblecobordismhypothesis
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This lecture volume argues that the global symmetries of a quantum field theory are not just groups acting on operators but the full network of topological defect operators, organized into a higher category. The five lecture series build the case: one introduces QFT as a functor and shows symmetries are topological operators; another develops anomalies as inflow from invertible theories; a third derives symmetry categories and exhibits the non-invertible chiral symmetry of massless QED; a fourth presents the cobordism hypothesis; and the fifth formalizes finite symmetry as a TFT-plus-boundary "quiche." If the picture is right, it means symmetries constrain QFT dynamics even when they are not group-like: anomalies force nontrivial infrared behavior, non-invertible defects impose selection rules, and fully extended TFTs are classified by dualizability.

What carries the argument

The load-bearing object is the topological defect operator: an operator or defect whose evaluation depends only on the homotopy class of its support, up to contact terms. Such operators can be fused, crossed, and shrunk, so they form a higher category where fusion is composition, junctions are morphisms, and the failure of topological invariance at coincident junctions is the anomaly. Two further machines carry the argument: the cobordism hypothesis, which classifies fully extended TFTs by fully dualizable objects, and the "quiche," an $(n+1)$-dimensional TFT together with a right topological boundary module, used to model abstract finite symmetry in field theory.

What would settle it

A concrete falsifier would be a QFT whose would-be symmetry defect has correlation functions that genuinely depend on the shape of its support even when separated from all other insertions, meaning the symmetry is not realizable by a topological operator.

Watch

Extended reading notes

Core claim

The volume's central claim is that generalized symmetries of quantum fields are topological operators, and that the collection of such operators in a $d$-dimensional QFT forms a $(d-1)$-dimensional higher tensor category. Conventional group-like symmetries are the special case of codimension-one invertible topological operators; higher-form and non-invertible symmetries are the same mechanism at other codimensions. The lectures develop the consequences: an anomalous theory is the boundary of an invertible field theory in one dimension higher, the ABJ-anomalous chiral symmetry of massless QED survives as a non-invertible defect with a computable higher structure, and finite symmetry in QFT can be abstracted as a topological field theory together with a boundary module.

Load-bearing premise

The argument that symmetries must organize into higher categories rests on the conjectural absence of global symmetries in a quantum theory of gravity, used to argue that all symmetries are emergent, and on the cobordism hypothesis as the classification of fully extended TFTs.

Editorial extensions

If this is right

  • Conventional 0-form symmetries are the codimension-one invertible topological operators, so all higher-form and non-invertible symmetries fall into the same framework.
  • Any anomalous theory is the boundary of an invertible field theory in one dimension higher, and a nonzero anomaly forbids a trivially gapped infrared phase.
  • Massless QED's chiral symmetry, though ABJ-anomalous, survives as a non-invertible topological defect with quantum dimension $1/\sqrt{N}$, and its fusion and associators produce physical Takahashi-Ward selection rules.
  • In 4d Yang-Mills at $\theta=\pi$ with even $N$, the mixed time-reversal and one-form symmetry anomaly forces the infrared to be either gapless or a nontrivial non-invertible TQFT.
  • Finite symmetry in QFT is abstractly a quiche, so gauging, duality defects, and the persistence of symmetry under RG flow become computations inside one topological structure.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If the topological-defect picture is right, the classification of QFTs can be attacked through their defect networks, and RG flow becomes a question of which higher categories survive to the infrared, a program the lectures only begin.
  • The framework suggests a model-building constraint: any exact symmetry in a low-energy effective theory must be emergent and therefore realized categorically, so exact symmetries are expected to be violated below the Planck scale.
  • The quiche formalism points toward a direct extension to continuous symmetries by replacing the finite homotopy spaces with Lie groupoids, an extension the lectures flag as open.
  • The relative Crane-Yetter viewpoint suggests a non-perturbative Chern-Simons partition function written as an integral over the character variety, a possibility the lectures state as an expectation rather than a result.
Share X Bluesky LinkedIn Reddit HN

Signed reviews

No signed human review yet.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

0 major / 8 minor

Summary. This volume compiles five sets of lecture notes from the 2022 Perimeter Institute and 2023 Les Diablerets summer schools on global categorical symmetries: Ohmori on symmetries in QFT, Córdova on anomalies, Del Zotto on symmetry categories with massless QED as the running example, Jordan on the cobordism hypothesis and fully extended TFTs, and Freed on a framework for finite symmetry in QFT via quiches and boundary theories. The unifying message is that generalized symmetries are topological operators and defects organized into higher categories, and that this structure constrains dynamics through anomaly matching, selection rules, and possible infrared phases. The volume is explicitly introductory and expository, aimed at newcomers with basic QFT and mathematical background.

Significance. As an expository volume, the main value is in making a large recent literature accessible and in working through concrete examples: the non-invertible chiral symmetry of massless QED built from the Hsin–Lam–Seiberg minimal TFT, the mixed time-reversal/one-form anomaly in SU(N) Yang–Mills at θ=π, fully extended WRT and Crane–Yetter theories, and the quiche formalism for finite symmetry. The notes are generally careful to flag conjectural statements, such as the heuristic gravity argument in §III.1.1, Conjecture IV.5.4 on pivotal structures, and Conjecture IV.5.8 on relative invertibility, and they give extensive references to the original literature. I specifically considered whether the reliance on the cobordism hypothesis and on the no-global-symmetries conjecture is load-bearing; on reading, the core worked examples are presented independently of these conjectures, so I do not see that dependence as a blocking correctness concern. The manuscript is a compilation of lecture notes rather than a research paper, and its soundness should be judged on internal consistency and clarity of exposition, at which it largely succeeds.

minor comments (8)
  1. [IV.2, Conjecture 2.2] The text labels the cobordism hypothesis a conjecture and then, from Lecture IV.3 onward, invokes it as the basis for theorems about dualizability and fully extended TFTs; please clarify which precise version is being used, for example the framed cobordism theorem established by Lurie versus the oriented or twisted generalizations, and state explicitly how much of the later discussion depends on that result.
  2. [III.2, Eq. (2.21)] Please state the normalization convention for the minimal TFT A_{N,p} when writing A_{N,1}(S^1×S^2, L_m), since the same TFT is normalized so that A_{N,p}(S^3)=1/√N; the displayed value 1 for m≡0 mod N is otherwise ambiguous.
  3. [III.2, Eqs. (2.11) and (2.15)] The Chern–Simons terms are written with missing wedge products, e.g. iN/(4π)∮ a da rather than iN/(4π)∮ a∧da; the same notational issue recurs in the definition of A_{N,1}.
  4. [I.4, Eq. (4.14)] There is a stray comma and a trailing '0' at the end of the displayed equation after ⟨0|W̃_R|0⟩; this appears to be an editing artifact and should be removed.
  5. [II.2.3] The heading 'Hypethesis/definition/theorem' should read 'Hypothesis/definition/theorem'.
  6. [III.1.1] The black-hole heuristic for the absence of global symmetries in quantum gravity is presented as a claim and then used to motivate the higher-category structure of symmetries; since the text itself notes that the no-global-symmetries statement is conjectural, an explicit sentence stating that the later examples, especially massless QED, do not depend on this conjecture would help newcomers.
  7. [IV.5] There are small language errors: 'Regardlessly' should be 'Regardless', and 'principle G-bundles' should be 'principal G-bundles'.
  8. [Preface] The preface and lecture notes refer to lectures by Shu-Heng Shao and Constantin Teleman that are not included in this volume; a brief note indicating where those omitted lectures are available would be helpful for readers.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the volume is expository, and its central claims are either working definitions or externally supported theorems, not derivations that reduce to their own inputs.

full rationale

The paper is a compilation of summer-school lecture notes, not a research claim with fitted parameters or closed derivation chains. Its central slogan, 'Generalised symmetries of quantum fields are topological operators' (Ohmori, Section I.1), is stated explicitly as a definition and a research program, and the lectures then illustrate it with concrete constructions, so there is no derivation that could reduce to its own input. The heuristic derivation of symmetry categories in Del Zotto's Lecture III.1 is self-labeled 'heuristic' and rests on the conjectural absence of global symmetries in quantum gravity; the main worked example, non-invertible chiral symmetry in massless QED, is instead derived from the ABJ anomaly (Equation III.2.3) and the Hsin-Lam-Seiberg decomposition of the relevant 3d TFT, none of which depends on the quantum-gravity conjecture. Jordan's lectures explicitly label the cobordism hypothesis as 'Conjecture 2.2' and cite dualizability results (Brochier-Jordan-Snyder, Gwilliam-Scheimbauer, and others) as published theorems; these self-citations are to independently proved results with stated assumptions, so they are real evidence rather than a load-bearing self-referential chain. No fitted input is renamed as a prediction, no uniqueness claim is imported from the authors' own prior work to force a conclusion, and no known result is repackaged under new coordinates as an organizing principle. The only definitional move, equating generalized symmetries with topological operators, is openly a definition and is followed by independent calculations, so even the strictest reading yields no circular step.

Assumptions & free parameters 0 free parameters · 4 assumptions · 0 invented entities

The volume is a review, so it does not introduce new free parameters or entities. It relies on standard and conjectural background, including the cobordism hypothesis and the no-global-symmetry conjecture. The most speculative ingredient is the no-global-symmetry conjecture, which underpins the heuristic derivation of higher categorical symmetry structure.

assumptions (4)
  • domain assumption Quantum field theories are defined as symmetric monoidal functors from bordism categories to vector spaces or higher categories.
    Used throughout the notes, e.g., Ohmori Section 2.1 and Jordan Section 1.1.
  • domain assumption The cobordism hypothesis (Lurie) holds, so fully extended TFTs are determined by fully dualizable objects.
    Stated as Conjecture 2.2 in Jordan's lectures and used to construct TFTs from algebraic data.
  • domain assumption Global symmetries are absent in any fundamental theory of quantum gravity.
    Used in Del Zotto's heuristic argument (Section III.1.1) to argue symmetries are emergent and organized into higher categories.
  • domain assumption Anomalies can be described by inflow from an invertible field theory in one higher dimension.
    Used in Córdova's lectures, stated as a hypothesis/definition/theorem in Section II.2.3.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Simons Lectures on Categorical Symmetries." pith.science (2026). https://pith.science/paper/GMEY4VCO

@misc{pith2026241109082,
  author       = {Pith},
  title        = {Pith review of: Simons Lectures on Categorical Symmetries},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/GMEY4VCO}},
  note         = {Machine review of arXiv:2411.09082}
}
read the original abstract

Global Categorical Symmetries are a powerful new tool for analyzing quantum field theories. This volume compiles lecture notes from the 2022 and 2023 summer schools on Global Categorical Symmetries, held at the Perimeter Institute for Theoretical Physics and at the Swiss Map Research Station in Les Diableret. Specifically, this volume collects the lectures: * An introduction to symmetries in quantum field theory, Kantaro Ohmori * Introduction to anomalies in quantum field theory, Clay C\'ordova * Symmetry Categories 101, Michele Del Zotto * Applied Cobordism Hypothesis, David Jordan * Finite symmetry in QFT, Daniel S. Freed These volumes are devoted to interested newcomers: we only assume (basic) knowledge of quantum field theory (QFT) and some relevant maths. We try to give appropriate references for non-standard materials that are not covered. Our aim in this first volume is to illustrate some of the main questions and ideas together with some of the methods and the techniques necessary to begin exploring global categorical symmetries of QFTs.

Figures

Figures reproduced from arXiv: 2411.09082 by the authors.

Figure 2
Figure 2. [PITH_FULL_IMAGE:figures/full_fig_p015_2.png] view at source ↗
Figure 3
Figure 3. [PITH_FULL_IMAGE:figures/full_fig_p019_3.png] view at source ↗
Figure 4
Figure 4. [PITH_FULL_IMAGE:figures/full_fig_p021_4.png] view at source ↗
Figures from the paper (51 more)
Figure 4
Figure 4. Figure 4 [PITH_FULL_IMAGE:figures/full_fig_p022_4.png]
Figure 4
Figure 4. Figure 4 [PITH_FULL_IMAGE:figures/full_fig_p023_4.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p027_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p028_1.png]
Figure 2
Figure 2. Figure 2 [PITH_FULL_IMAGE:figures/full_fig_p033_2.png]
Figure 2
Figure 2. Figure 2 [PITH_FULL_IMAGE:figures/full_fig_p035_2.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p044_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p047_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p048_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p049_1.png]
Figure 2
Figure 2. Figure 2 [PITH_FULL_IMAGE:figures/full_fig_p054_2.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p058_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p059_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p060_3.png]
Figure 4
Figure 4. Figure 4 [PITH_FULL_IMAGE:figures/full_fig_p062_4.png]
Figure 4
Figure 4. Figure 4 [PITH_FULL_IMAGE:figures/full_fig_p064_4.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p081_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p082_3.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p108_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p109_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p110_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p111_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p112_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p113_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p114_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p115_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p116_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p120_1.png]
Figure 1
Figure 1. Figure 1 [PITH_FULL_IMAGE:figures/full_fig_p121_1.png]
Figure 2
Figure 2. Figure 2 [PITH_FULL_IMAGE:figures/full_fig_p126_2.png]
Figure 2
Figure 2. Figure 2 [PITH_FULL_IMAGE:figures/full_fig_p136_2.png]
Figure 2
Figure 2. Figure 2 [PITH_FULL_IMAGE:figures/full_fig_p141_2.png]
Figure 2
Figure 2. Figure 2 [PITH_FULL_IMAGE:figures/full_fig_p142_2.png]
Figure 2
Figure 2. Figure 2 [PITH_FULL_IMAGE:figures/full_fig_p144_2.png]
Figure 2
Figure 2. Figure 2 [PITH_FULL_IMAGE:figures/full_fig_p145_2.png]
Figure 2
Figure 2. Figure 2 [PITH_FULL_IMAGE:figures/full_fig_p146_2.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p149_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p150_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p151_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p152_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p153_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p154_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p155_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p162_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p163_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p164_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p165_3.png]
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p167_3.png]
Figure 4
Figure 4. Figure 4 [PITH_FULL_IMAGE:figures/full_fig_p174_4.png]
Figure 4
Figure 4. Figure 4 [PITH_FULL_IMAGE:figures/full_fig_p175_4.png]
Figure 4
Figure 4. Figure 4 [PITH_FULL_IMAGE:figures/full_fig_p177_4.png]

Discussion (0). Continue with ORCID to comment.

Forward citations

Cited by 16 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Understanding Non-Split 2-Group Symmetry: (3+1)D SymTFT, Anomaly and Bordism

    hep-th 2026-08 conditional novelty 7.0 of 10

    For G=(Z2,Z2,triv,1), the authors classify anomalies via oriented and spin bordism in spacetime dimensions d<=5 and derive the (3+1)D SymTFT boundary conditions, including the equivalence of the anomalous symmetry cat...

  2. Entanglement in Presence of Topological Interfaces and Dualities

    hep-th 2026-07 conditional novelty 7.0 of 10

    Duality interfaces in 2d CFT project the vacuum entanglement spectrum onto a single symmetry sector, making the interface itself a physical symmetry-resolution filter.

  3. On Quantum Aspects of 1-Form Symmetries II: Bordism, Invertible Phases, and Anomalies

    hep-th 2026-06 unverdicted novelty 7.0 of 10

    Bordism computation for K(Z,3) identifies a new mixed perturbative anomaly in 5D and a new Z2 discrete anomaly in 7D for U(1) 1-form symmetries.

  4. Generalized Families of QFTs

    hep-th 2026-02 unverdicted novelty 7.0 of 10

    Generalized family anomalies for broken higher-group and non-invertible symmetries constrain RG flows and IR phases of QFT families, with explicit application to deformed 4d QCD.

  5. The Line, the Strip and the Duality Defect

    hep-th 2026-02 unverdicted novelty 7.0 of 10

    The XY-plaquette model is claimed to possess a continuous SO(2) non-invertible duality symmetry at arbitrary coupling, realized by open condensation defects in its symmetry TFT.

  6. Strange correlator and string order parameter for non-invertible symmetry protected topological phases in 1+1d

    cond-mat.str-el 2025-05 conditional novelty 7.0 of 10

    Strange correlators and string order parameters for non-invertible SPT phases in 1+1d are systematically constructed from the interface algebra, giving local detectors of these phases.

  7. SymTFT, Protected Gaplessness, and Spontaneous Breaking of Non-invertible Symmetries

    hep-th 2025-04 conditional novelty 7.0 of 10

    The authors classify, via Galois theory of cyclotomic polynomials, when finite duality symmetry groups of 4d BF-type SymTFTs admit invariant Lagrangian boundary conditions, thereby determining when symmetry-preserving...

  8. SymTFTs and Non-Invertible Symmetries of 6d (2,0) SCFTs of Type $D$ from M-theory

    hep-th 2024-12 conditional novelty 7.0 of 10

    The 7d SymTFT for 6d (2,0) D_N SCFTs is derived from M-theory on AdS7 × RP4, including the outer-automorphism Z2 sector, and is used to derive non-invertible symmetries and anomaly polynomials.

  9. Tilts from 2-Groups

    hep-th 2026-08 conditional novelty 6.0 of 10

    Line operators charged under the 1-form part of a 2-group symmetry must generically break the 0-form part, enforced by a family anomaly derived from Wess-Zumino consistency.

  10. Non-invertible symmetries in the axiverse, and the imaginary wormholes

    hep-th 2026-06 unverdicted novelty 6.0 of 10

    Imaginary wormholes and the IDB imply that towers of BPS EFT instantons generate infinitely many superpotential terms that break non-invertible axion shift symmetries in N=1 axiverse models.

  11. Notes on (-2)-form symmetries

    hep-th 2026-06 unverdicted novelty 6.0 of 10

    Introduces (-2)-form symmetries that modify the SymTFT action to relate QFTs differing by anomaly data or non-invertible symmetry associators, illustrated in 2D-4D models, fusion categories, club-sandwich RG flows, an...

  12. SymTFT for Continuous Symmetries: Non-linear Realizations and Spontaneous Breaking

    hep-th 2025-09 conditional novelty 6.0 of 10

    Continuous-symmetry SymTFTs are extended to non-linear coset realizations and to spontaneous breaking using boundary and corner constructions, recovering CCWZ actions and SSB Ward identities.

  13. SymTFT actions, Condensable algebras and Categorical anomaly resolutions

    hep-th 2025-09 conditional novelty 6.0 of 10

    For Q8 and Rep(Q8), the paper computes condensable algebras, identifies intrinsically gapless SPT phases, and derives fusion-category short exact sequences that resolve categorical anomalies.

  14. Is Crane--Yetter fully extended?

    math-ph 2025-06 conditional novelty 6.0 of 10

    Fully extended invertible 4D TQFTs valued in braided fusion categories form a Z/6-extension of the Witt group, so Crane-Yetter has six inequivalent point-refinements for fixed modular data.

  15. Non-Invertible Symmetries as Condensation Defects in Finite-Group Gauge Theories

    cond-mat.str-el 2024-12 conditional novelty 6.0 of 10

    Non-invertible symmetries in finite-group gauge theories are realized as condensation defects, with a complete Z_N dictionary and new automorphism symmetry expressions.

  16. SymTFTs for $U(1)$ symmetries from descent

    hep-th 2024-11 conditional novelty 6.0 of 10

    Symmetry descent is extended from discrete to continuous U(1) higher-form symmetries, yielding SymTFTs that match the Antinucci-Benini and Brennan-Sun constructions.

Reference graph

Works this paper leans on

6 extracted references · 6 linked inside Pith · cited by 16 Pith papers

  1. [1]

    pair of pants

    dentifies each link ∂ ¯νp, p∈Z, with the standard sphereSℓ−1. Assuming enough finiteness,σ(Sℓ−1)∈Ωℓ−1C defines101 an (m−ℓ + 1)-dimensional field theory σ (ℓ−1)—the dimensional reduction of σ alongSℓ−1— and a local defect δp determines a left boundary theory δ(ℓ−1) forσ (ℓ−1), again 101The looping ΩC of the symmetric monoidal n-category C is the symmetric mono...

  2. [4]

    (First verify that d(H) is normal in K.) Assume that A andG are finite groups

    A crossed module is the following data: a pair of groups (H,K ), a homomorphism d :H→K, and an action of K onH such that for all h,h′,h′′∈H andk∈K we have d(h′)·h′′ =h′h′′(h′)−1 d(k·h) =kd (h)k−1 DefineA = kerd andG = cokerd. (First verify that d(H) is normal in K.) Assume that A andG are finite groups. (a) Prove that A is a subgroup of the center of H. In ...

  3. [7]

    character dual

    The bihomomorphism b induces homomorphisms A→ (A′)∨ and A′→A∨; the non- degeneracy condition states that these are isomorphisms. Here A∨ is the Pontrjagin dual abelian group of homomorphisms A→ C×. The duality relation is symmetric: (A∨)∨ A (canonically). Remark 4.3. For any finite abelian group A there is a canonical duality pairing (evalu- ation) A∨×A→ C...

  4. [107]

    Fix a positive integern and finiten-dimensional symmetry data (σ,ρ )

    The basic idea is to execute the quotient construction on a submanifold, not necessarily to take the quotient of the entire theory. Fix a positive integern and finiten-dimensional symmetry data (σ,ρ ). Suppose ϵ is an augmentation of σ , as in De finition 3.3. As explained in De finition 3.4, if (eF,θ ) is a (σ,ρ )-module structure on an n-dimensional quantu...

  5. [115]

    1-form A-symmetry

    3.14 Symmetry data Let A be a finite abelian group, set X =B2A, and fix a basepoint ∗→ B2A. This defines the semiclassical data of a BA-symmetry , what is often referred to as a “1-form A-symmetry”. We set λ = 0: there is no ’t Hooft anomaly. For de finiteness set n = 4, so we use the 5-dimensional finite homotopy theory σ =σ (5) B2A. The basepoint gives a reg...

  6. [117]

    answers” to the short range “questions

    The main argument is in 4.18. T rivially gapped theories with finite symmetry In quantum field theory one is often interested in the low energy , or quantum relativisti- cally equivalent 118 long distance, behavior of a system. As with classical physics, posed in terms of di fferential equations, a quantum field theory is formulated at short dis- tance/time a...

Pith tools

Reviewed August 12, 2026 · model on record in the stance chip above.