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We prove delocalization of eigenvectors of vertex-transitive graphs via elementary estimates of the spectral projector. We recover in this way known results which were formerly proved using representation theory. Similar techniques show…

Spectral Theory · Mathematics 2025-10-15 Nicolas Burq , Cyril Letrouit

In this study, we present two results that relate Tutte polynomials. First, we provide new and complete polynomial invariants for graphs. We note that the number of variables of our polynomials is one. Second, let L_1 and L_2 be two…

Combinatorics · Mathematics 2020-10-06 Misaki Kume , Tsuyoshi Miezaki , Tadashi Sakuma , Hidehiro Shinohara

We study both $H$ and $E/Z$-eigenvalues of the adjacency tensor of a uniform multi-hypergraph and give conditions for which the largest positive $H$ or $Z$-eigenvalue corresponds to a strictly positive eigenvector. We also investigate when…

Spectral Theory · Mathematics 2012-09-26 Kelly J. Pearson , Tan Zhang

We say that a graph $H$ dominates another graph $H'$ if the number of homomorphisms from $H'$ to any graph $G$ is dominated, in an appropriate sense, by the number of homomorphisms from $H$ to $G$. We study the family of dominating graphs,…

Combinatorics · Mathematics 2024-11-27 David Conlon , Joonkyung Lee

We show that several dichotomy theorems concerning the second level of the Borel hierarchy are special cases of the $\aleph_0$-dimensional generalization of the open graph dichotomy, which itself follows from the usual proof(s) of the…

Logic · Mathematics 2018-03-09 Raphaël Carroy , Benjamin D. Miller , Dániel T. Soukup

Understanding the structure of a graph along with the structure of its subgraphs is important for several problems in graph theory. Two examples are the Reconstruction Conjecture and isomorph-free generation. This paper raises the question…

Combinatorics · Mathematics 2009-09-18 Stephen G. Hartke , Hannah Kolb , Jared Nishikawa , Derrick Stolee

If $G$ is a looped graph, then its adjacency matrix represents a binary matroid $M_{A}(G)$ on $V(G)$. $M_{A}(G)$ may be obtained from the delta-matroid represented by the adjacency matrix of $G$, but $M_{A}(G)$ is less sensitive to the…

Combinatorics · Mathematics 2013-09-04 Robert Brijder , Hendrik Jan Hoogeboom , Lorenzo Traldi

We introduce and investigate multivariate Tutte polynomials, dichromatic polynomials, subset-corank polynomials, size-corank polynomials, and rank generating polynomials of semimatroids, which generalize the corresponding polynomial…

Combinatorics · Mathematics 2025-08-04 Houshan Fu

It is well known that the 2-variable Tutte polynomials contain chromatic polynomial and flow polynomial of graphs, i.e. the cases of $y=0$ and $x=0$. In 2013, K\'{a}lm\'{a}n introduced the interior and exterior polynomials which generalized…

Combinatorics · Mathematics 2026-05-26 Tianlong Ma , Xiaxia Guan , Xian'an Jin

Let $\Gamma$ denote a bipartite distance-regular graph with diameter $D \ge 4$ and valency $k \ge 3$. Let $X$ denote the vertex set of $\Gamma$, and let $A$ denote the adjacency matrix of $\Gamma$. For $x \in X$ let $T=T(x)$ denote the…

Combinatorics · Mathematics 2016-11-23 Mark S. MacLean , Stefko Miklavic

In this paper we discuss reconstruction problems for graphs. We develop some new ideas like isomorphic extension of isomorphic graphs, partitioning of vertex sets into sets of equivalent points, subdeck property, etc. and develop an…

General Mathematics · Mathematics 2011-10-21 Dhananjay P. Mehendale

Using the graphs of prisms and Tutte Fragments, we construct an infinite family of hamiltonian and non-hamiltonian graphs in which Tutte's counterexample to Tait's conjecture appears in a certain sense as a minimal element. We observe that…

Combinatorics · Mathematics 2026-04-23 Herbert Fleischner , Enrico Iurlano , Günther R. Raidl

We construct the geometric Langlands functor in one direction (from the automorphic to the spectral side) in characteristic zero settings (i.e., de Rham and Betti). We prove that various forms of the conjecture (de Rham vs Betti, restricted…

Algebraic Geometry · Mathematics 2025-10-02 Dennis Gaitsgory , Sam Raskin

In this note we generalize the convolution formula for the Tutte polynomial of Kook-Reiner-Stanton and Etienne-Las Vergnas to a more general setting that includes both arithmetic matroids and delta-matroids. As corollaries, we obtain new…

Combinatorics · Mathematics 2017-04-24 Spencer Backman , Matthias Lenz

A graph drawing in the plane is called an almost embedding if the images of any two non-adjacent simplices (i.e. vertices or edges) are disjoint. Almost embeddings (more precisely, their higher-dimensional analogues) naturally appear in…

Geometric Topology · Mathematics 2026-03-10 E. Alkin , A. Miroshnikov , A. Skopenkov

This paper deals with adjacency matrices of signed cycle graphs and chemical descriptors based on them. The eigenvalues and eigenvectors of the matrices are calculated and their efficacy in classifying different signed cycles is determined.…

Combinatorics · Mathematics 2016-10-18 A. M. Mathai , Thomas Zaslavsky

We generalize the structure theorem of Robertson and Seymour for graphs excluding a fixed graph $H$ as a minor to graphs excluding $H$ as a topological subgraph. We prove that for a fixed $H$, every graph excluding $H$ as a topological…

Data Structures and Algorithms · Computer Science 2015-03-19 Martin Grohe , Dániel Marx

We prove that every point-determining digraph $D$ contains a vertex $v$ such that $D-v$ is also point determining. We apply this result to show that for any $\{0,1\}$-matrix $M$, with $k$ diagonal zeros and $\ell$ diagonal ones, the size of…

Combinatorics · Mathematics 2013-08-05 Pavol Hell , César Hernández-Cruz

This paper extends the Bakry-\'{E}mery theorem connecting the Ricci curvature and log-Sobolev inequalities to the matrix-valued setting. Using tools from noncommuative geometry, it is shown that for a right invariant second order…

Mathematical Physics · Physics 2020-07-01 Haojian Li , Marius Junge , Nicholas LaRacuente

The graph reconstruction conjecture asserts that every finite simple graph on at least three vertices can be reconstructed up to isomorphism from its deck - the collection of its vertex-deleted subgraphs. Kocay's Lemma is an important tool…

Combinatorics · Mathematics 2014-09-09 Igor C. Oliveira , Bhalchandra D. Thatte