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We analyze combinatorial structures which play a central role in determining spectral properties of the volume operator in loop quantum gravity (LQG). These structures encode geometrical information of the embedding of arbitrary valence…

General Relativity and Quantum Cosmology · Physics 2010-11-22 Johannes Brunnemann , David Rideout

A graph is chordal if every cycle of length at least four has a chord. In 1961, Dirac characterized chordal graphs as those graphs that can be built from complete graphs by repeated clique-sums. Generalizing this, we consider the class of…

Combinatorics · Mathematics 2024-05-03 James Dylan Douthitt , James Oxley

A bipartite graph $G=(V,E)$ with $V=V_1\cup V_2$ is biregular if all the vertices of each stable set, $V_1$ and $V_2$, have the same degree, $r$ and $s$, respectively. This paper studies difference sets derived from both Abelian and…

Combinatorics · Mathematics 2024-04-09 G. Araujo-Pardo , C. Dalfó , M. A. Fiol , N. López

In [7], Higashitani, Kummer, and Micha{\l}ek pose a conjecture about the symmetric edge polytopes of complete multipartite graphs and confirm it for a number of families in the bipartite case. We confirm that conjecture for a number of new…

Combinatorics · Mathematics 2024-04-03 Max Kölbl

In two seminal papers Kontsevich used a construction called_graph homology_ as a bridge between certain infinite dimensional Lie algebras and various topological objects, including moduli spaces of curves, the group of outer automorphisms…

Quantum Algebra · Mathematics 2010-08-25 Jim Conant , Karen Vogtmann

We present a form of algebraic reasoning for computational objects which are expressed as graphs. Edges describe the flow of data between primitive operations which are represented by vertices. These graphs have an interface made of…

Logic in Computer Science · Computer Science 2010-07-23 Lucas Dixon , Ross Duncan , Aleks Kissinger

The modelling of interconnection networks by graphs motivated the study of several extremal problems that involve well known parameters of a graph (degree, diameter, girth and order) and ask for the optimal value of one of them while…

Combinatorics · Mathematics 2020-05-07 Gabriela Araujo-Pardo , Nacho López

An embedding of a graph on an orientable surface is orientably-regular (or rotary, in an equivalent terminology) if the group of orientation-preserving automorphisms of the embedding is transitive (and hence regular) on incident vertex-edge…

Combinatorics · Mathematics 2023-11-17 Stefan Gyurki , Sona Pavlikova , Jozef Siran

We define an algebraic setup of homology for hypergraphs, which defaults to simplicial homology in the case of graphs, and study its basic properties. As part of our study we define algebraic spanning trees of hypergraphs, along with…

Combinatorics · Mathematics 2021-09-07 Reinhard Diestel

We study various binomial and monomial ideals arising in the theory of divisors, orientations, and matroids on graphs. We use ideas from potential theory on graphs and from the theory of Delaunay decompositions for lattices to describe…

Combinatorics · Mathematics 2015-11-24 Fatemeh Mohammadi , Farbod Shokrieh

Finite element codes typically use data structures that represent unstructured meshes as collections of cells, faces, and edges, each of which require associated coordinate systems. One then needs to store how the coordinate system of each…

Numerical Analysis · Mathematics 2021-02-16 Rainer Agelek , Michael Anderson , Wolfgang Bangerth , William Barth

In this paper, firstly, we provide some necessary and sufficient conditions for generalized Cayley graphs on abelian groups to be bipartite. Secondly, we deduce several necessary and sufficient conditions for generalized Cayley graphs on…

Combinatorics · Mathematics 2024-12-18 Liao Qianfen , Liu Weijun , Zhang Pengli

Recently, neural network architectures have been developed to accommodate when the data has the structure of a graph or, more generally, a hypergraph. While useful, graph structures can be potentially limiting. Hypergraph structures in…

Algebraic Topology · Mathematics 2020-12-14 Eric Bunch , Qian You , Glenn Fung , Vikas Singh

The aim of the paper is to clarify the nature of combinatorial structures associated with maps on closed compact surfaces. We prove that maps give rise to Lagrangian matroids representable in a setting provided by cohomology of the surface…

Combinatorics · Mathematics 2007-05-23 Richard F. Booth , Alexandre V. Borovik , Israel Gelfand

Let B_{2t} be a bipartite planar graph with an even number of regions. We are able to find bounds for the graded Betti numbers and the projective dimension of the quotient ring associated to the graph. We also will investigate the minimal…

Commutative Algebra · Mathematics 2024-04-01 Maurizio Imbesi , Monica La Barbiera

It is known that the Levi graph of any rank two coset geometry is an edge-transitive graph, and thus coset geometries can be used to construct many edge transitive graphs. In this paper, we consider the reverse direction. Starting from…

Algebraic Geometry · Mathematics 2011-06-30 Julie De Saedeleer , Dimitri Leemans , Mark Mixer , Tomaž Pisanski

We initiate the study of computational complexity of graph coverings, aka locally bijective graph homomorphisms, for {\em graphs with semi-edges}. The notion of graph covering is a discretization of coverings between surfaces or topological…

Discrete Mathematics · Computer Science 2025-10-09 Jan Bok , Jiří Fiala , Petr Hliněný , Nikola Jedličková , Jan Kratochvíl

The fundamental role of on-shell diagrams in quantum field theory has been recently recognized. On-shell diagrams, or equivalently bipartite graphs, provide a natural bridge connecting gauge theory to powerful mathematical structures such…

High Energy Physics - Theory · Physics 2015-06-17 Sebastian Franco , Daniele Galloni , Alberto Mariotti

We present statistics on the decompositions (with respect to a distinguished symmetric 2t-cycle) of vertices of the hypercube graph, whose negative parts are covered by two subsets of the ground set {1,...,t} of the corresponding oriented…

Combinatorics · Mathematics 2023-03-24 Andrey O. Matveev

A bipartite graph $G=(A, B, E)$ is said to be a biconvex bipartite graph if there exist orderings $<_A$ in $A$ and $<_B$ in $B$ such that the neighbors of every vertex in $A$ are consecutive with respect to $<_B$ and the neighbors of every…

Combinatorics · Mathematics 2024-06-04 Dhanyamol Antony , Anita Das , Shirish Gosavi , Dalu Jacob , Shashanka Kulamarva