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Categories can be identified -- up to isomorphism -- with polynomial comonads on Set. The left Kan extension of a functor along itself is always a comonad -- called the density comonad -- so it defines a category when its carrier is…

Category Theory · Mathematics 2025-04-28 David I. Spivak

Poly-bicategories generalise planar polycategories in the same way as bicategories generalise monoidal categories. In a poly-bicategory, the existence of enough 2-cells satisfying certain universal properties (representability) induces…

Category Theory · Mathematics 2019-09-30 Amar Hadzihasanovic

We prove the boundedness of complements modulo two conjectures: Borisov-Alexeev conjecture and effective adjunction for fibre spaces. We discuss the last conjecture and prove it in two particular cases.

Algebraic Geometry · Mathematics 2010-04-26 Yu. G. Prokhorov , V. V. Shokurov

In the present paper, we derive an adjunction formula for the Grauert-Riemenschneider canonical sheaf of a singular hypersurface V in a complex manifold M. This adjunction formula is used to study the problem of extending L2-cohomology…

Complex Variables · Mathematics 2013-04-09 Jean Ruppenthal , Håkan Samuelsson Kalm , Elizabeth Wulcan

Several monads of probability measures have been shown to have presentations as codensity monads over small categories of stochastic maps. This paper studies how three key properties of these probability monads, relevant to categorical…

Category Theory · Mathematics 2026-03-11 Zev Shirazi

In this paper we show that the strict and lax pullbacks of a 2-categorical opfibration along an arbitrary 2-functor are homotopy equivalent. We give two applications. First, we show that the strict fibers of an opfibration model the…

Category Theory · Mathematics 2021-05-18 Nick Gurski , Niles Johnson , Angélica M. Osorno

We define locally wide finitary 2-categories by relaxing the definition of finitary 2-categories to allow infinitely many objects and isomorphism classes of 1-morphisms and infinite dimensional hom-spaces of 2-morphisms. After defining…

Category Theory · Mathematics 2021-06-24 James Macpherson

We prove that the monoidal 2-category of cospans of finite linear orders and surjections is the universal monoidal category with an object X with a semigroup and a cosemigroup structures, where the two structures satisfy a certain…

Category Theory · Mathematics 2007-06-12 M. Menni , N. Sabadini , R. F. C. Walters

In this paper, I prove a very general extension theorem for log pluricanonical systems. The main application of this extension theorem is (together with Kawamata's subadjunction theorem) to give an optimal subadjunction theorem which…

Algebraic Geometry · Mathematics 2007-11-05 Hajime Tsuji

We construct a finitary additive 2-category whose Grothendieck ring is isomorphic to the semigroup algebra of the monoid of order-decreasing and order-preserving transformations of a finite chain.

Representation Theory · Mathematics 2017-05-10 Anna-Louise Grensing , Volodymyr Mazorchuk

We prove the Morrison-Kawamata cone conjecture for klt Calabi-Yau pairs in dimension 2. That is, for a large class of rational surfaces as well as K3 surfaces and abelian surfaces, the action of the automorphism group of the surface on the…

Algebraic Geometry · Mathematics 2019-12-19 Burt Totaro

Two adjoint functors can be seen as generalisations of the two functions within a Galois connection. If instead the adjoints are not generalised from functions, but from relations, then analogously the object of study becomes a more general…

Category Theory · Mathematics 2025-02-10 Phillip-Jan van Zyl

We give an overview of the parts of arXiv:2004.04279 that deal with 2-categories, up to and including adjunction, and explain how the Segal-type approach to 2-categories adopted there is related to the more standard approaches. As an…

Algebraic Geometry · Mathematics 2021-02-03 D. Kaledin

In this paper, we study Clifford algebra construction from the perspective of adjunctions motivated by the general framework of Krashen and Lieblich. We introduce a category of weighted polynomial laws whose associated Clifford algebra…

Algebraic Geometry · Mathematics 2025-10-28 Nguyen Xuan Bach

We introduce a general construction on 2-monads. We develop background on maps of 2-monads, their left semi-algebras, and colimits in 2-category. Then, we introduce the construction of a colimit induced by a map of 2-monads, show that we…

Category Theory · Mathematics 2021-02-09 Martin Hyland , Christine Tasson

This text is dedicated to the development of the theory of $(\infty,\omega)$-categories. We present generalizations of standard results from category theory, such as the lax Grothendieck construction, the Yoneda lemma, lax (co)limits and…

Category Theory · Mathematics 2024-11-26 Félix Loubaton

We provide a calculus of mates for functors to the $\infty$-category of $\infty$-categories and extend Lurie's unstraightening equivalences to show that (op)lax natural transformations correspond to maps of (co)cartesian fibrations that do…

Category Theory · Mathematics 2024-04-04 Rune Haugseng , Fabian Hebestreit , Sil Linskens , Joost Nuiten

We study the bicategory of Landau-Ginzburg models, which has potentials as objects and matrix factorisations as 1-morphisms. Our main result is the existence of adjoints in this bicategory and a description of evaluation and coevaluation…

Algebraic Geometry · Mathematics 2015-12-10 Nils Carqueville , Daniel Murfet

We study codensity monads $T$ induced by (mostly small, mostly dense) full subcategories $A \subset K$. These monads behave quite similarly, we show some connections with the Isbell duality, pro-finite objects and compact spaces. We prove…

Category Theory · Mathematics 2025-08-05 Ivan Di Liberti

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