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In this article we describe properties of the 2-functor from the 2-category of comonads to the 2-category of functors that sends a comonad to its forgetful functor. This allows us to describe contexts where algebras over a monad are…

Category Theory · Mathematics 2022-05-04 Brice Le Grignou

Game comonads have brought forth a new approach to studying finite model theory categorically. By representing model comparison games semantically as comonads, they allow important logical and combinatorial properties to be exressed in…

Category Theory · Mathematics 2022-09-05 Samson Abramsky , Tomáš Jakl , Thomas Paine

We show that contrary to common belief in the DisCoCat community, a monoidal category is all that is needed to define a categorical compositional model of natural language. This relies on a construction which freely adds adjoints to a…

Category Theory · Mathematics 2020-09-16 Antonin Delpeuch

We introduce a notion of complexity of diagrams (and in particular of objects and morphisms) in an arbitrary category, as well as a notion of complexity of functors between categories equipped with complexity functions. We discuss several…

Category Theory · Mathematics 2020-07-01 Saugata Basu , M. Umut Isik

We specialise a recently introduced notion of generalised dinaturality for functors $T : (\mathcal{C}^\text{op})^p \times \mathcal{C}^q \to \mathcal{D}$ to the case where the domain (resp., codomain) is constant, obtaining notions of ends…

Category Theory · Mathematics 2023-03-03 Fosco Loregian , Emily de Oliveira Santos

Prolongations of a group extension can be studied in a more general situation that we call group extensions of the co-type of a crossed module. Cohomology classification of such extensions is obtained by applying the obstruction theory of…

Category Theory · Mathematics 2015-03-17 Nguyen Tien Quang

The notion of Kan extendable subcategories was initially introduced to define the category of compactly generated fibrewise topological spaces over a T1 base space and to establish its cartesian closure. In this paper, we show that the same…

Category Theory · Mathematics 2025-11-14 Moncef Ghazel , Inès Saihi , Walid Taamallah

Graduated locally finitely presentable categories are introduced, examples include categories of sets, vector spaces, posets, presheaves and Boolean algebras. A finitary functor between graduated locally finitely presentable categories is…

Category Theory · Mathematics 2024-02-06 Jirí Adámek , Lurdes Sousa

Combinatorial categories satisfy a stronger form of Yoneda Lemma, namely, the isomorphism type of an object can be recovered by counting the number of homomorphisms from all other objects into it. In this work, we show that this property…

Category Theory · Mathematics 2025-09-23 Antonio Ceres , Cristina Costoya , Antonio Viruel

Every smooth manifold contains particles which propagate. These form objects and morphisms of a category equipped with a functor to the category of Abelian groups, turning this into a 0+1 topological field theory. We investigate the…

Symplectic Geometry · Mathematics 2009-06-26 Jean-Yves Welschinger

It is well known that to give an oplax functor of bicategories $\mathbf{1}\to\mathscr{C}$ is to give a comonad in $\mathscr{C}$. Here we generalize this fact, replacing the terminal bicategory by any bicategory $\mathscr{A}$ for which the…

Category Theory · Mathematics 2018-05-07 Charles Walker

Kan extensions provide a natural general framework for a variety of combinatorial problems. We have developed rewriting procedures for Kan extensions (over the category of sets) and this enables one program to address a wide range of…

Combinatorics · Mathematics 2007-05-23 Anne Heyworth

Clones are specializations of operads forming powerful instruments to describe varieties of algebras wherein repeating variables are allowed in their equations. They allow us in this way to realize and study a large range of algebraic…

Combinatorics · Mathematics 2026-04-08 Samuele Giraudo

It is well-known that biological phenomena are emergent. Emergent phenomena are quite interesting and amazing. However, they are difficult to be understood. Due to this difficulty, we propose a theory to describe emergence based on a…

Category Theory · Mathematics 2018-10-30 Giuliano Gadioli La Guardia , Pedro Jeferson Miranda

We study locally constant coefficients. We first study the theory of homotopy Kan extensions with locally constant coefficients in model categories, and explain how it characterizes the homotopy theory of small categories. We explain how to…

Algebraic Topology · Mathematics 2009-12-12 Denis-Charles Cisinski

We consider sets with infinite addition, called $\Sigma$-monoids, and contribute to their literature in three ways. First, our definition subsumes those from previous works and allows us to relate them in terms of adjuctions between their…

Category Theory · Mathematics 2025-01-22 Pablo Andrés-Martínez , Chris Heunen

If $\mathcal{C}$ is a cocomplete monoidal category in which tensoring from both sides preserves coequalizers, then the category of monoids over $\mathcal{C}$ is cocomplete. The same holds if $\mathcal{C}$ has regular factorizations and…

Category Theory · Mathematics 2018-07-03 Hans-E. Porst

We use the terms "$\infty$-categories" and "$\infty$-functors" to mean the objects and morphisms in an "$\infty$-cosmos." Quasi-categories, Segal categories, complete Segal spaces, naturally marked simplicial sets, iterated complete Segal…

Category Theory · Mathematics 2019-09-23 Emily Riehl , Dominic Verity

This chapter describes interrelations between: (1) algebraic structure on sets of scalars, (2) properties of monads associated with such sets of scalars, and (3) structure in categories (esp. Lawvere theories) associated with these monads.…

Rings and Algebras · Mathematics 2011-11-01 Dion Coumans , Bart Jacobs

For any length category, we establish a set of rules (necessary and sufficient) that ensure a partial order on the isomorphism classes of simple objects such that the category is equivalent to the category of finite dimensional…

Representation Theory · Mathematics 2026-04-07 Henning Krause