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We improve the existing lower bounds on the order of counterexamples to a conjecture by P. Schmid, determine some properties of the possible counterexamples of minimum order for each prime, and the isomorphism type of the center of the…

Group Theory · Mathematics 2022-11-03 Jaime Calles , José Cantarero , Juan Omar Gómez , Gustavo Ortega

Extending the discovery by Giles Gardam of a concrete counterexample to Kaplansky's unit conjecture in characteristic 2, a family of counterexamples for every prime characteristic is presented.

Rings and Algebras · Mathematics 2021-06-07 Alan G. Murray

Since the transformative workshop by the American Institute of Mathematics on the minimum rank of a graph, two longstanding open problems have captivated the community interested in the minimum rank of graphs: the graph complement…

Combinatorics · Mathematics 2025-06-02 Francesco Barioli , Shaun M. Fallat , Himanshu Gupta , Zhongshan Li

We propose a Nordhaus-Gaddum conjecture for $q(G)$, the minimum number of distinct eigenvalues of a symmetric matrix corresponding to a graph $G$: for every graph $G$ excluding four exceptions, we conjecture that $q(G)+q(G^c)\le |G|+2$,…

Spectral Theory · Mathematics 2018-07-18 Rupert H. Levene , Polona Oblak , Helena Šmigoc

In this paper we prove the following results (via a unified approach) for all sufficiently large $n$: (i) [$1$-factorization conjecture] Suppose that $n$ is even and $D\geq 2\lceil n/4\rceil -1$. Then every $D$-regular graph $G$ on $n$…

Combinatorics · Mathematics 2014-10-23 Béla Csaba , Daniela Kühn , Allan Lo , Deryk Osthus , Andrew Treglown

The Tree Decomposition Conjecture by Bar\'at and Thomassen states that for every tree $T$ there exists a natural number $k(T)$ such that the following holds: If $G$ is a $k(T)$-edge-connected simple graph with size divisible by the size of…

Combinatorics · Mathematics 2016-03-02 Martin Merker

Although there are many simple proofs of Jordan's decomposition theorem in the literature (see [1], the references mentioned there, and [2]), our proof seems to be even more elementary. In fact, all we need is the theorem on the dimensions…

History and Overview · Mathematics 2007-05-23 Pawel Kroeger

In this article we develop counterexamples to the Hasse principle using only techniques from undergraduate number theory and algebra. By keeping the technical prerequisites to a minimum, we hope to provide a path for nonspecialists to this…

Number Theory · Mathematics 2011-09-01 Wayne Aitken , Franz Lemmermeyer

The Calogero-Moser families are partitions of the irreducible characters of a complex reflection group derived from the block structure of the corresponding restricted rational Cherednik algebra. It was conjectured by Martino in 2009 that…

Representation Theory · Mathematics 2014-09-29 Ulrich Thiel

In this paper we prove an explicit matching theorem for some Hecke elements in the case of (possibly ramified) cyclic base change for general linear groups over local fields of characteristic zero with odd residue characteristic under a…

Number Theory · Mathematics 2023-03-14 Takuya Yamauchi

We prove a Jordan decomposition theorem for minimal connected simple groups of finite Morley rank with non-trivial Weyl group. From this, we deduce a precise structural description of Borel subgroups of this family of simple groups. Along…

Logic · Mathematics 2010-09-17 Tuna Altinel , Jeffrey Burdges , Oliver Frecon

Aiming for a revival of the theory of crystallographic complex reflection groups, we compute (minimal) Coxeter-like reflection presentations for the infinite families of those non-genuine groups which satisfy Steinberg's fixed point…

Group Theory · Mathematics 2025-10-10 Davide Dal Martello

We prove that the Herzog-Sch\"onheim Conjecture holds for any group $G$ of order smaller than $1440$. In other words we show that in any non-trivial coset partition $\{g_i U_i\}_{i=1}^n $ of $G$ there exist distinct $1 \leq i, j \leq n$…

Group Theory · Mathematics 2018-03-12 Leo Margolis , Ofir Schnabel

Recently, W. M. Schmidt and L. Summerer introduced a new theory which allowed them to recover the main known inequalities relating the usual exponents of Diophantine approximation to a point in $\mathbb{R}^n$, and to discover new ones. They…

Number Theory · Mathematics 2016-04-26 Damien Roy

This is the first in a series of papers on rank decompositions of the matrix multiplication tensor. In this paper we: establish general facts about rank decompositions of tensors, describe potential ways to search for new matrix…

Computational Complexity · Computer Science 2016-10-27 Luca Chiantini , Christian Ikenmeyer , J. M. Landsberg , Giorgio Ottaviani

In this note, we prove that every even regular multigraph on $n$ vertices with multiplicity at most $r$ and minimum degree at least $rn/2 + o(n)$ has a Hamilton decomposition. This generalises a result of Vaughan who proved an asymptotic…

Combinatorics · Mathematics 2023-12-18 Vincent Pfenninger

Given a linear map $T$ on a Euclidean Jordan algebra of rank $n$, we consider the set of all nonnegative vectors $q$ in $R^n$ with decreasing components that satisfy the pointwise weak-majorization inequality…

Functional Analysis · Mathematics 2020-08-18 Muddappa Gowda , Jeong Juyoung

In 2014, Keevash proved the existence of $(n,q,r)$-Steiner systems (equivalently $K_q^r$-decompositions of $K_n^r$) for all large enough $n$ satisfying the necessary divisibility conditions. In 2021, Glock, K\"uhn, and Osthus proposed a…

Combinatorics · Mathematics 2025-12-04 Cicely Henderson , Luke Postle

The exceptional complex reflection groups of rank 2 are partitioned into three families. We construct explicit matrix models for the Hecke algebras associated to the maximal groups in the tetrahedral and octahedral family, and use them to…

Representation Theory · Mathematics 2025-03-10 Eirini Chavli , Götz Pfeiffer

We provide a constructive proof of the Seymour Second Neighborhood Conjecture (SSNC) by reframing the problem as a set-packing optimization problem. The universal family of oriented graphs $\mathcal{O}$ is classified by their minimum…

Combinatorics · Mathematics 2026-02-24 Charles N. Glover