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Hans Zassenhaus conjectured that every torsion unit of the integral group ring of a finite group $G$ is conjugate within the rational group algebra to an element of the form $\pm g$ with $g\in G$. This conjecture has been disproved recently…

Group Theory · Mathematics 2019-02-19 Mauricio Caicedo , Ángel del Río

It is shown that if T is a connected nontrivial graph and X is an arbitrary finite simplicial complex, then there is a graph G such that the complex Hom(T,G) is homotopy equivalent to X. The proof is constructive, and uses a nerve lemma.…

Combinatorics · Mathematics 2007-05-23 Anton Dochtermann

We show that the homotopy category of injective $A$-modules is generically trivial if and only if the derived category of all modules is generically trivial for an algebra $A$. Moreover we show some connections between the generic objects,…

Representation Theory · Mathematics 2014-12-05 Zhe Han

We give the first tractable and systematic examples of nontrivial higher digraph homotopy groups. To do this we define relative digraph homotopy groups and show these satisfy a long exact sequence analogous to the relative homotopy groups…

Algebraic Topology · Mathematics 2025-04-08 Stephen Theriault , Jie Wu , Shing-Tung Yau , Mengmeng Zhang

We report on some computational experiments related to the trivial units property and unique product property for group rings of torsion-free groups. These properties are related to Kaplansky's unit and zero-divisor conjectures. Our…

Group Theory · Mathematics 2026-03-26 Heiko Dietrich , Melissa Lee , Andre Nies , Marc Vinyals

Although intersection homology lacks a ring structure, certain expressions (called uniform) in the intersection homology of an irreducible projective variety $X$ always give the same value, when computed via the decomposition theorem on any…

Algebraic Geometry · Mathematics 2007-05-23 Jonathan Fine

We give a detailed exposition of the homotopy theory of equivalence relations, perhaps the simplest nontrivial example of a model structure.

Algebraic Topology · Mathematics 2009-09-06 Finnur Larusson

Tate cohomology has been generalised by several authors using different constructions that have applications in group theory, ring theory and homotopical algebra. Therefore, there is a need for a uniform account that explains why their…

Group Theory · Mathematics 2026-04-02 Max Gheorghiu

We give an elementary proof of the Hurewicz theorem relating homotopy and homology groups of a cubical Kan complex. Our approach is based on the notion of a loop space of a cubical set, developed in a companion paper ``Homotopy groups of…

Algebraic Topology · Mathematics 2024-09-09 Daniel Carranza , Chris Kapulkin , Andrew Tonks

The objective of this work is to reconsider the schematization problem of [6], with a particular focus on the global case over Z. For this, we prove the conjecture [Conj. 2.3.6][15] which gives a formula for the homotopy groups of the…

Algebraic Geometry · Mathematics 2024-04-17 Bertrand Toën

The object of this paper is to examine finite solvable groups whose integral group rings have only trivial central units.

Rings and Algebras · Mathematics 2018-06-21 Sugandha Maheshwary

We investigate the homotopy type of a certain homogeneous space for a simple complex algebraic group. We calculate some of its classical topological invariants and introduce a new one. We also propose several conjectures about its…

Algebraic Topology · Mathematics 2026-03-24 Dylan Johnston , Dmitriy Rumynin

The aim of this paper is to show that the most elementary homotopy theory of $\mathbf{G}$-spaces is equivalent to a homotopy theory of simplicial sets over $\mathbf{BG}$, where $\mathbf{G}$ is a fixed group. Both homotopy theories are…

Category Theory · Mathematics 2020-04-15 Amit Sharma

Using the Luthar-Passi method, we investigate the classical Zassenhaus conjecture for the normalized unit group of the integral group ring of the Higman-Sims simple sporadic group HS. As a consequence, we confirm the Kimmerle's conjecture…

Rings and Algebras · Mathematics 2007-05-23 V. A. Bovdi , A. B. Konovalov

We study unit groups of rings of the form $\mathbb{F}_2[x,y]/(y^2 + gy + h)$, for $g, h \in \mathbb{F}_2[x]$ -- in particular, the question of (non)triviality of such unit groups. Up to automorphisms of $\mathbb{F}_2[x,y]$ we classify such…

Commutative Algebra · Mathematics 2025-10-16 Justin Chen , Vishal Muthuvel

Let $G$ be a simply-connected simple compact Lie group and let $M$ be an orientable smooth closed 4-manifold. In this paper we calculate the homotopy type of the suspension of $M$ and the homotopy types of the gauge groups of principal…

Algebraic Topology · Mathematics 2018-06-12 Tse Leung So

This is an introduction to the study of abstract homotopy theory by means of model categories and $(\infty,1)$-categories. The only prerequisites are very basic general topology and abstract algebra. None categorical background is needed.…

Algebraic Topology · Mathematics 2020-08-13 Yuri Ximenes Martins

Let $R$ be a commutative ring with unit. We consider the homotopy theory of the category of spectral sequences of $R$-modules with the class of weak equivalences given by those morphisms inducing a quasi-isomorphism at a certain fixed page.…

Algebraic Topology · Mathematics 2023-02-22 Muriel Livernet , Sarah Whitehouse

In this paper we study the global structure of the stable homotopy theory of spectra. We establish criteria for when the homotopy theory associated to a given stable model category agrees with the classical stable homotopy theory of…

Algebraic Topology · Mathematics 2020-01-13 Stefan Schwede , Brooke Shipley

This paper defines homology in homotopy type theory, in the process stable homotopy groups are also defined. Previous research in synthetic homotopy theory is relied on, in particular the definition of cohomology. This work lays the…

Logic · Mathematics 2018-12-27 Robert Graham