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We identify the class of elementary groups: the smallest class of totally disconnected locally compact second countable (t.d.l.c.s.c.) groups that contains the profinite groups and the discrete groups, is closed under group extensions of…

Group Theory · Mathematics 2015-06-12 Phillip Wesolek

We prove that every locally Cartesian closed $\infty$-category with subobject classifier has a strict initial object and disjoint and universal binary coproducts.

Category Theory · Mathematics 2022-02-15 Jonas Frey , Nima Rasekh

We compute the collection of CW-complexes in the model category of small categories constructed by Joyal and Tierney. More generally, if $X$ is a connected topological space, we show that the homotopy category of CW-complexes in…

Category Theory · Mathematics 2017-11-27 Christian Frank , Andrew Salch

We characterize simple complex abelian varieties and simple abelian surfaces in terms of primitivity of translation automorphisms. Applying this together with a result due to Diller and Favre, we then classify all primitive birational…

Algebraic Geometry · Mathematics 2014-12-16 Keiji Oguiso

In this paper, we discuss certain circumstances in which the category of tame functors inherits an abelian category structure with minimal resolutions and a model category structure with minimal cofibrant replacements. We also present a…

Algebraic Topology · Mathematics 2024-03-26 Wojciech Chachólski , Barbara Giunti , Claudia Landi , Francesca Tombari

We prove group existence and structure theorems in a general setting of tame topological theories. More precisely, we identify a linear/non-linear dividing line -- called topological 1-basedness -- among the class of t-minimal theories with…

Logic · Mathematics 2025-08-27 Benjamin Castle , Assaf Hasson , Will Johnson

We develop the formal theory of monads, as established by Street, in univalent foundations. This allows us to formally reason about various kinds of monads on the right level of abstraction. In particular, we define the bicategory of monads…

Logic in Computer Science · Computer Science 2025-02-26 Niels van der Weide

Many definitions of weak and strict $\infty$-categories have been proposed. In this paper we present a definition for $\infty$-categories with strict associators, but which is otherwise fully weak. Our approach is based on the existing type…

Category Theory · Mathematics 2021-09-06 Eric Finster , Alex Rice , Jamie Vicary

We provide a formulation of the univalence axiom in a universe category model of dependent type theory that is convenient to verify in homotopy-theoretic settings. We further develop a strengthening of the univalence axiom, called pointed…

Logic in Computer Science · Computer Science 2025-12-19 Chris Kapulkin , Yufeng Li

We axiomatically define (pre-)Hilbert categories. The axioms resemble those for monoidal Abelian categories with the addition of an involutive functor. We then prove embedding theorems: any locally small pre-Hilbert category whose monoidal…

Category Theory · Mathematics 2010-08-05 Chris Heunen

We prove that the category of countable Tate modules over an arbitrary discrete ring embeds fully faithfully into that of condensed modules. If the base ring is of finite type, we characterize the essential image as generated by the free…

Category Theory · Mathematics 2025-01-23 Valerio Melani , Hugo Pourcelot , Gabriele Vezzosi

We define a general class of dependent type theories, encompassing Martin-L\"of's intuitionistic type theories and variants and extensions. The primary aim is pragmatic: to unify and organise their study, allowing results and constructions…

Logic · Mathematics 2020-09-14 Andrej Bauer , Philipp G. Haselwarter , Peter LeFanu Lumsdaine

In this paper we construct classifying localic categories and groupoids for various bundles equipped with logical structure. When these bundles are local homeomorphisms, we recover the localic groupoids that classify geometric theories,…

Category Theory · Mathematics 2026-05-25 Graham Manuell , Joshua L. Wrigley

We introduce a very natural topology on the set of total orderings of monomials of any algebra having a countable basis over a field. This topological space and some notable subspaces are compact. This topological framework allows us to…

Rings and Algebras · Mathematics 2011-06-02 Roberto Boldini

We prove that every separable tracial von Neumann algebra embeds into a II$_1$ factor with property (T) which can be taken to have trivial outer automorphism and fundamental groups. We also establish an analogous result for the trivial…

Operator Algebras · Mathematics 2022-05-17 Ionut Chifan , Daniel Drimbe , Adrian Ioana

Constructing and manipulating homotopy types from categorical input data has been an important theme in algebraic topology for decades. Every category gives rise to a `classifying space', the geometric realization of the nerve. Up to weak…

Algebraic Topology · Mathematics 2019-10-30 Stefan Schwede

We give a model of dependent type theory with one univalent universe and propositional truncation interpreting a type as a stack, generalising the groupoid model of type theory. As an application, we show that countable choice cannot be…

Logic in Computer Science · Computer Science 2017-04-21 Thierry Coquand , Bassel Mannaa , Fabian Ruch

For a finite dimensional algebra $A$, we establish correspondences between torsion classes and wide subcategories in $mod(A)$. In case $A$ is representation finite, we obtain an explicit bijection between these two classes of subcategories.…

Representation Theory · Mathematics 2017-06-19 Frederik Marks , Jan Stovicek

Theorem (after Giraud, SGA 4): Suppose $A$ is a simplicial category. The following conditions are equivalent: (i) There is a cofibrantly generated closed model category $M$ such that $A$ is equivalent to the Dwyer-Kan simplicial…

Algebraic Topology · Mathematics 2007-05-23 Carlos Simpson

We prove that every topologically transitive shift of finite type in one dimension is topologically conjugate to a subshift arising from a primitive random substitution on a finite alphabet. As a result, we show that the set of values of…

Dynamical Systems · Mathematics 2020-04-15 Philipp Gohlke , Dan Rust , Timo Spindeler