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Let $n\geq 2$ and $G_n=\mathbb{Z}^n\rtimes SL_n(\mathbb{Z})$. We classify all $G_n$-invariant von Neumann subalgebras in $L(G_n)$. For $n=2$, this gives an alternative proof of the previous result of Jiang-Liu. For $n\geq 3$, this gives the…

Operator Algebras · Mathematics 2026-01-13 Yongle Jiang , Hongyi Li

This paper is concerned with long-time interest of us, especially, the author, in realizing graphs as Reeb graphs of real algebraic functions of certain nice classes. The Reeb graph of a differentiable function is the set consisting of all…

Algebraic Geometry · Mathematics 2025-09-05 Naoki Kitazawa

The intersection of a complex plane curve with a small three-sphere surrounding one of its singularities is a non-trivial link. The refined punctual Hilbert schemes of the singularity parameterize subschemes supported at the singular point…

Algebraic Geometry · Mathematics 2019-12-19 Alexei Oblomkov , Vivek Shende

In this paper, we contribute to the Kuperberg program by giving a diagrammatic presentation of generators and relations for the affine $E_7$ unshaded subfactor planar algebra. Using this presentation, we prove that its jellyfish algorithm…

Quantum Algebra · Mathematics 2026-01-15 Melody Molander

Let $R$ be a commutative ring with identity and a fixed invertible element $q^{\frac{1}{2}}$. Let $\mathcal{S}_n$ denote the Kauffman bracket skein algebra of the $n$-holed disk $\Sigma_{0,n+1}$ over $R$. When $q+q^{-1}$ is invertible, in…

Geometric Topology · Mathematics 2026-04-23 Haimiao Chen

There is a natural construction which associates to a finitely generated, countable, discrete group $G$ and a 3-cocycle $\omega$ of $G$ an inclusion of II$_1$ factors, the so-called diagonal subfactors (with cocycle). In the case when the…

Operator Algebras · Mathematics 2008-12-30 Dietmar Bisch , Paramita Das , Shamindra Kumar Ghosh

Median graphs are connected graphs in which for all three vertices there is a unique vertex that belongs to shortest paths between each pair of these three vertices. In this paper we provide several novel characterizations of planar median…

Combinatorics · Mathematics 2021-10-19 Carsten R. Seemann , Vincent Moulton , Peter F. Stadler , Marc Hellmuth

Given graphs $G$ and $H$, we propose a method to implicitly enumerate topological-minor-embeddings of $H$ in $G$ using decision diagrams. We show a useful application of our method to enumerating subgraphs characterized by forbidden…

Data Structures and Algorithms · Computer Science 2019-11-19 Yu Nakahata , Jun Kawahara , Takashi Horiyama , Shin-ichi Minato

Graph product structure theory expresses certain graphs as subgraphs of the strong product of much simpler graphs. In particular, an elegant formulation for the corresponding structural theorems involves the strong product of a path and of…

Data Structures and Algorithms · Computer Science 2022-04-26 Michael A. Bekos , Giordano Da Lozzo , Petr Hliněný , Michael Kaufmann

Characterizing derived equivalences between algebras via combinatorial structures has recently become a popular topic. In this paper, we study admissible fractional Brauer graph algebras, a new subclass of self-injective special biserial…

Representation Theory · Mathematics 2026-04-09 Bohan Xing

We describe an algorithm for classifying the closed subsets of a root system, up to conjugation by the associated Weyl group. Such a classification of an irreducible root system is closely related to the classification of the regular…

Rings and Algebras · Mathematics 2019-03-15 Andrew Douglas , Willem A. de Graaf

The Subgraph Isomorphism problem asks, given a host graph G on n vertices and a pattern graph P on k vertices, whether G contains a subgraph isomorphic to P. The restriction of this problem to planar graphs has often been considered. After…

Discrete Mathematics · Computer Science 2015-03-19 Paul Bonsma

We consider the problem of constructing bounded-degree planar geometric spanners of Euclidean and unit-disk graphs. It is well known that the Delaunay subgraph is a planar geometric spanner with stretch factor $C_{del\approx 2.42$; however,…

Data Structures and Algorithms · Computer Science 2008-02-21 Iyad A. Kanj , Ljubomir Perkovic

Let $\Sigma$ be a surface with negative Euler characteristic, genus at least one and at most one boundary component. We prove that the skein algebra of $\Sigma$ over the field of rational functions can be algebraically generated by a finite…

Geometric Topology · Mathematics 2024-08-28 Ramanujan Santharoubane

The min-rank of a graph was introduced by Haemers (1978) to bound the Shannon capacity of a graph. This parameter of a graph has recently gained much more attention from the research community after the work of Bar-Yossef et al. (2006). In…

Combinatorics · Mathematics 2016-11-26 Son Hoang Dau , Yeow Meng Chee

We revisit Haagerup's enigmatic reduction theorem \cite[Theorems 2.1 \& 3.1]{HJX} showing how that theorem may be extended to general von Neumann algebras $\M$ equipped with an arbitrary faithful normal semifinite weight in a manner which…

Operator Algebras · Mathematics 2025-06-10 Louis Labuschagne , Quanhua Xu

We present a method for associating labeled directed graphs to finite-dimensional Lie algebras, thereby enabling rapid identification of key structural algebraic features. To formalize this approach, we introduce the concept of…

Mathematical Physics · Physics 2026-01-23 Tim Heib , David Edward Bruschi

We introduce the notion of extended admissible dissections of a marked surface, building upon the notion of an admissible dissection of a marked surface by Amiot--Plamondon--Schroll. For each extended admissible dissection we construct a…

Representation Theory · Mathematics 2026-03-18 Marina Godinho , Dave Murphy

We introduce the general polynomial algebras characterizing a class of higher order superintegrable systems that separate in Cartesian coordinates. The construction relies on underlying polynomial Heisenberg algebras and their defining…

Mathematical Physics · Physics 2023-07-20 Danilo Latini , Ian Marquette , Yao-Zhong Zhang

This paper is a contribution to the study of the subgroup structure of exceptional algebraic groups over algebraically closed fields of arbitrary characteristic. Following Serre, a closed subgroup of a semisimple algebraic group $G$ is…

Group Theory · Mathematics 2017-12-22 Adam R. Thomas