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Polynomial functors are a categorical generalization of the usual notion of polynomial, which has found many applications in higher categories and type theory: those are generated by polynomials consisting a set of monomials built from sets…

Logic in Computer Science · Computer Science 2021-12-30 Eric Finster , Samuel Mimram , Maxime Lucas , Thomas Seiller

We establish natural splittings for the values of global Mackey functors at orthogonal, unitary and symplectic groups. In particular, the restriction homomorphisms between the orthogonal, unitary and symplectic groups of adjacent dimensions…

Algebraic Topology · Mathematics 2022-08-09 Stefan Schwede

In this article we study cohomological properties of the category of polynomial outer functors on free groups, which are the functors from the category of finitely generated free groups to the category of rational vector spaces which send…

Algebraic Topology · Mathematics 2025-08-06 Louis Hainaut

A description of the derived functors of Lie functors for free abelian groups is given.

Algebraic Topology · Mathematics 2018-08-03 Roman Mikhailov

In this paper, we give a description of polynomial functors from (finitely generated free) groups to abelian groups in terms of non-linear Mackey functors generalizing those given in a paper of Baues-Dreckmann-Franjou-Pirashvili published…

Algebraic Topology · Mathematics 2012-09-12 Manfred Hartl , Teimuraz Pirashvili , Christine Vespa

We show that extension groups between two polynomial functors on free groups are the same in the category of all functors and in a subcategory of polynomial functors of bounded degree. We give some applications. ---- On montre que les…

K-Theory and Homology · Mathematics 2014-09-03 Aurélien Djament , Teimuraz Pirashvili , Christine Vespa

We study the category of polynomial functors from finitely generated free groups to a stable infinity-category D. We show that this category is equivalent to the category of excisive functors from pointed animas to D, and also to truncated…

Algebraic Topology · Mathematics 2025-05-22 Gregory Arone

Motivated in part by the study of the stable homology of automorphism groups of free groups, we consider cohomological calculations in the category $\mathcal{F}(\textbf{gr})$ of functors from finitely generated free groups to abelian…

Algebraic Topology · Mathematics 2018-04-04 Christine Vespa

We consider several types of non-existence theorems for functors. For example, there are no nontrivial functors from the category of groups (or the category of pointed sets, or vector spaces) to any small category. Another type of questions…

Category Theory · Mathematics 2025-05-20 Emmanuel Dror Farjoun , Sergei O. Ivanov , Aleksandr Krasilnikov , Anatolii Zaikovskii

We consider the semigroup $Ext(A,B)$ of extensions of a separable C*-algebra $A$ by a stable C*-algebra $B$ modulo unitary equivalence and modulo asymptotically split extensions. This semigroup contains the group $Ext^{-1/2}(A,B)$ of…

Operator Algebras · Mathematics 2007-05-23 V. Manuilov , K. Thomsen

An approach to identify the normal subgroups determined by ideals in free group rings with the help of the derived functors of non-additive functors is explored. A similar approach, i.e., via derived functors, for computing limits of…

Group Theory · Mathematics 2016-05-27 Roman Mikhailov , Inder Bir S. Passi

We study polynomial functors over locally cartesian closed categories. After setting up the basic theory, we show how polynomial functors assemble into a double category, in fact a framed bicategory. We show that the free monad on a…

Category Theory · Mathematics 2015-05-13 Nicola Gambino , Joachim Kock

We establish a decomposition of stable homology of automorphism groups of free groups with polynomial contravariant coefficients in term of functor homology. This allows several explicit computations, intersecting results obtained by…

Algebraic Topology · Mathematics 2019-08-15 Aurélien Djament

We study polynomial functors in the incompressible category $\text{Ver}_4^+$, which can be viewed as super polynomial functors in characteristic 2. Concretely, we classify additive, exact and simple polynomial functors, and describe how…

Representation Theory · Mathematics 2026-03-16 Kevin Coulembier , Serina Hu

We give examples of quaternion and octonion division algebras over a field $F$ of characteristic $2$ that split over a purely inseparable extension $E$ of $F$ of degree $\geq 4$ but that do not split over any subextension of $F$ inside $E$…

Rings and Algebras · Mathematics 2020-12-18 Detlev W. Hoffmann

We develop a theory of separable ring extensions and separable functors for nonunital rings in the setting of firm modules. We prove nonunital analogues of classical results on functorial separability and semisimplicity, and apply these…

Rings and Algebras · Mathematics 2026-05-26 Patrik Lundström

We develop a functorial approach to the study of the homotopy groups of spheres and Moore spaces $M(A,n)$, based on the Curtis spectral sequence and the decomposition of Lie functors as iterates of simpler functors such as the symmetric or…

Algebraic Topology · Mathematics 2014-10-01 Lawrence Breen , Roman Mikhailov

In this paper, we discuss the motivic stable homotopy type of abelian varieties. For an abelian variety over a perfect field $k$ with a rational point, it always splits off a top-dimensional cell in motivic stable homotopy category…

Algebraic Geometry · Mathematics 2025-07-09 Haoyang Liu

It is known algebraically that any abelian group is a direct sum of a divisible group and a reduced group (See Theorem 21.3 of \cite{Fuchs:abelian-group}). In this paper, conditions to split off rational parts in homotopy types from a given…

Algebraic Topology · Mathematics 2007-05-23 Norio Iwase , Nobuyuki Oda

This paper presents a description of the fourth dimension quotient, using the theory of limits of functors from the category of free presentations of a given group to the category of abelian groups. A functorial description of a quotient of…

Group Theory · Mathematics 2017-03-27 Roman Mikhailov , Inder Bir S. Passi
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