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Let $G$ be a finite group and $A$ be a regular local ring on which $G$ acts. Under certain assumptions on $A$ and the action, Serre defined a function $a_G\colon G\rightarrow\mathbb{Z}$ which can be viewed as a higher dimensional analogue…

Number Theory · Mathematics 2025-06-16 Tomoyuki Abe

We show that pointlike sets are decidable for the pseudovariety of finite semigroups whose idempotent-generated subsemigroup is R-trivial. Notably, our proof is constructive: we provide an explicit relational morphism which computes the…

Group Theory · Mathematics 2022-04-21 Karsten Henckell , Samuel Herman

We consider constrained Horn clause solving from the more general point of view of solving formula equations. Constrained Horn clauses correspond to the subclass of Horn formula equations. We state and prove a fixed-point theorem for Horn…

Logic in Computer Science · Computer Science 2021-09-13 Stefan Hetzl , Johannes Kloibhofer

We introduce the notion of a Tits arrangement on a convex open cone as a special case of (infinite) simplicial arrangements. Such an object carries a simplicial structure similar to the geometric representation of Coxeter groups. The…

Combinatorics · Mathematics 2015-06-01 Michael Cuntz , Bernhard Mühlherr , Christian J. Weigel

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

Let $X$ be a cubic fourfold in $P^5_{C}$. We prove that, assuming the Hodge conjecture for the product $S \times S$, where $S$ is a complex surface, and the finite dimensionality of the Chow motive $h(S)$, there are at most a countable…

Algebraic Geometry · Mathematics 2017-01-23 Claudio Pedrini

Let $\mathcal C$ be a class of topological semigroups. A semigroup $X$ is called (1) $\mathcal C$-$closed$ if $X$ is closed in every topological semigroup $Y\in\mathcal C$ containing $X$ as a discrete subsemigroup, (2) $ideally$ $\mathcal…

Group Theory · Mathematics 2023-01-09 Taras Banakh , Serhii Bardyla

This paper provides an overview of Lawvere's Fixed-Point Theorem in category theory and aims to detail the universal framework underlying self-reference and recursive structures. First, we rigorously define fundamental concepts - such as…

General Mathematics · Mathematics 2025-05-19 Joaquim Reizi Barreto

For a topological space $X$ a topological contraction on $X$ is a closed mapping $f:X\to X$ such that for every open cover of $X$ there is a positive integer $n$ such that the image of the space $X$ via the $n$th iteration of $f$ is a…

General Topology · Mathematics 2026-02-04 Michał Morayne , Robert Rałowski

We establish the Hodge conjecture for the top dimensional cohomology group with integer coefficients of any $q$-complete complex manifold $X$ with $q<\dim X$. This holds in particular for the complement $X=\mathbb{C}\mathbb{P}^n\setminus A$…

Algebraic Geometry · Mathematics 2016-03-09 Franc Forstneric , Jaka Smrekar , Alexandre Sukhov

Suppose that $\{T_{a}:a\in G\}$ is a group of uniformly $L$-Lipschitzian mappings with bounded orbits $\left\{T_{a}x:a\in G\right\}$ acting on a hyperconvex metric space $M$. We show that if $L<\sqrt{2}$, then the set of common fixed points…

Functional Analysis · Mathematics 2016-12-20 Andrzej Wiśnicki , Jacek Wośko

The first author has recently shown that semisimple algebraic groups are classified up to motivic equivalence by the local versions of the classical Tits indexes over field extensions, known as Tits p-indexes. We provide in this article the…

Algebraic Geometry · Mathematics 2017-09-26 Charles De Clercq , Skip Garibaldi

Inverse limits, unlike direct limits, can in general be void, [1]. The existence of fixed points for arbitrary mappings $T : X \longrightarrow X$ is conjectured to be equivalent with the fact that related direct limits of all finite…

General Mathematics · Mathematics 2007-09-05 Elemer E Rosinger

In this article we discuss a possibility to implement a well-known scheme of proof for contraction mapping theorems in a situation, when convergence, families of Cauchy sequences, and contractiveness of mappings are defined axiomatically.…

Functional Analysis · Mathematics 2023-07-13 Vladyslav Babenko , Vira Babenko , Oleg Kovalenko

A group of bijections G acting on a set X is said with fixed points (abbreviated as gaf from the french "groupe {\`a} points fixes") if any element of G has at least one fixed point in X. The G group is said with a common fixed point…

Group Theory · Mathematics 2019-01-28 Guido Ahumada , Bernard Brighi , Nicolas Chevallier , Augustin Fruchard

A discrete subset $S$ of a topologically gyrogroup $G$ is called a {\it suitable set} for $G$ if $S\cup \{1\}$ is closed and the subgyrogroup generated by $S$ is dense in $G$, where $1$ is the identity element of $G$. In this paper, we…

General Topology · Mathematics 2025-08-19 Jiamin He , Jiajia Yang , Fucai Lin

Based on the recently developed theory of random sequential compactness, we prove the random Kakutani fixed point theorem in random normed modules: if G is a random sequentially compact L0-convex subset of a random normed module, then every…

Functional Analysis · Mathematics 2025-10-07 Qiang Tu , Xiaohuan Mu , Tiexin Guo , Guang Yang , Yuanyuan Sun

The paper contains constructions of Hilbert systems for the action of the circle group $T$ using subgroups of implementable Bogoljubov unitaries w.r.t. Fock representations of the Fermion algebra for suitable data of the selfdual framework:…

Mathematical Physics · Physics 2009-10-31 H. Baumgaertel , A. L. Carey

We prove a theorem of Tits type for automorphism groups of projective varieties over an algebraically closed field of arbitrary characteristic, which was first conjectured by Keum, Oguiso and Zhang for complex projective varieties.

Algebraic Geometry · Mathematics 2021-02-24 Fei Hu , Tomohide Terasoma

We prove that if a group scheme of multiplicative type acts on an algebraic stack with affine, finitely presented diagonal then the stack of fixed points is algebraic. For this, we extend two theorems of [SGA3.2] on functors of subgroups of…

Algebraic Geometry · Mathematics 2021-01-08 Matthieu Romagny