Markus Zetto

I am a PhD researcher at the University of Hamburg, working with David Reutter. I work on higher category theory, homotopy theory, and extended topological field theories.

I submitted my thesis, Cauchy-completions and higher fusion categories, in September 2026.

In November 2026, I will join the Max Planck Institute for Mathematics in Bonn.

Portrait of Markus Zetto

Papers & preprints

2026Preprint

Enriched ∞-operads as marked algebras

An enriched ∞-operad can be recovered from its category of right modules, together with a marking by the representable ones. This reduces their study to the theory of presentably symmetric monoidal module categories. I use this description to prove, for enrichment in spaces, an equivalence between algebras in symmetric sequences and Lurie’s definition of ∞-operads, that also identifies the respective categories of algebras.

2025Preprint

Enriched ∞-categories as marked module categories

We prove that an enriched ∞-category is determined by its enriched presheaf category, together with a marking by the representable presheaves. This description reduced enriched ∞-category theory to the study of presentable module categories. For instance, we recover the tensor product of enriched categories from the cocompleted tensor product on presentable categories, and give a very model-independent account of univalence (Rezk-completeness).

Also: Higher tensor categories and their extensions — joint Scottish Talbot notes (2025).

Doctoral thesis

Cauchy-completions and higher fusion categories

University of Hamburg · Supervisor: David Reutter · Submitted 23 September 2026

My thesis studies higher fusion categories using enriched ∞-category theory. More precisely, it characterizes the Morita category of separable multifusion categories as a higher Cauchy-completions of the trivial k-linear n-category B^n k, and shows that it consists of precisely the fully dualizable objects in the Morita-category of n-idempotent-complete k-linear n-categories.

The main result shows that higher idempotent-completion preserves adjoints at all categorical levels. By the Cobordism Hypothesis, the resulting fully dualizable objects determine fully extended framed topological field theories.

Abstract and thesis details

Research interests

My main interests are in higher category theory and its applications to topology and mathematical physics.

Higher category theory

I study enriched ∞-categories and ∞-operads, including their descriptions through marked presentable categories. Other aspects of my work include weighted colimits, profunctors, and Cauchy-completion.

Fusion categories & TFTs

I study higher fusion categories and their relation to extended topological field theories. My work uses higher Cauchy-completion to characterize these categories and establish full dualizability.

Sheaves and stratified topology

I am interested in constructible sheaves, Verdier duality, and the algebraic L-groups of stratified spaces, including their relation to stratified surgery theory.

Factorization algebras and field theory

I study the relationship between the BV formalism and constructible factorization algebras, and how these constructions extend from manifolds to stratified spaces.

Past conferences & workshops2021–2025
Time Name Place
11.–15.08.2025Masterclass: Infinity Operads and Applications to GeometryCopenhagen, Denmark
20.–27.07.2025Conference: Spaces of Tensor CategoriesEdinburgh, Great Britain
29.06.–05.07.2025European Talbot — Higher algebra and chromatic homotopy theoryKolding, Denmark
24.–27.02.2025Workshop on Gray Products and Lax ConstructionsRaitenhaslach, Germany
16.–21.02.2025Cobordism categories Masterclass: Building bridges between algebra and geometryCopenhagen, Denmark
22.–28.09.2024 Scottish Talbot On Algebra and Topology - "Higher tensor categories and their extensions" Glenmore, Scotland
09.-13.09.2024 Workshop on "Dualisable Categories & Continuous K-theory" Bonn, Germany
10.-14.06.2024 Masterclass: Continuous K-theory, dualizable and rigid categories Copenhagen, Denmark
15.-19.04.2024 (∞,n)-Categories and their applications Utrecht, Netherlands
08.-09.04.2024 Bavarian Geometry & Topology Meeting XII Regensburg, Germany
19.01.2024 16th Seminar on Conformal Field Theory Darmstadt, Germany
18.-22.09.2023 Conference on Characteristic Classes and Singular Spaces Kiel, Germany
14.-18.08.2023 Higher Structures in Functorial Field Theory Regensburg, Germany
19.-23.06.2023 Hausdorff School: TQFTs and their connections to representation theory and mathematical physics Bonn, Germany
22.-24.03.2023 Higher categorical methods in algebra and geometry Hamburg, Germany
18.-22.07.2022 Domoschool 2022: Gauge Theory and the Langlands Program Domodossola, Italy
04.-08.10.2021 Pure Spinors, Superalgebras, and Holomorphic Twists Heidelberg, Germany
12.-16.07.2021 Junior Researchers Conference: Higher Structures in QFT and String Theory Online

Contact

markus.zetto@uni-hamburg.de

Currently in Hamburg

University of Hamburg
Room 4.32 · Bundesstraße 55
20146 Hamburg, Germany

+49 40 42838 5305

From November 2026
Max Planck Institute for Mathematics, Bonn