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We study an abstract notion of tree structure which lies at the common core of various tree-like discrete structures commonly used in combinatorics: trees in graphs, order trees, nested subsets of a set, tree-decompositions of graphs and…

Combinatorics · Mathematics 2017-02-28 Reinhard Diestel

We note here that the problem of determining extremal values of Sombor index for trees with a given degree sequence fits within the framework of results by Hua Wang from [Cent. Eur. J. Math. 12 (2014) 1656-1663], implying that the greedy…

Combinatorics · Mathematics 2024-05-20 Ivan Damnjanović , Marko Milošević , Dragan Stevanović

A subtree can be induced in a natural way by a subset of leaves of a rooted tree. We study the number of nonisomorphic such subtrees induced by leaves (leaf-induced subtrees) of a rooted tree with no vertex of outdegree 1 (topological…

Combinatorics · Mathematics 2022-06-30 Audace A. V. Dossou-Olory , Ignatius Boadi

For a graph $G$, an edge-separating (resp. vertex-separating) path system of $G$ is a family of paths in $G$ such that for any pair of edges $e_1, e_2$ (resp. pair of vertices $v_1, v_2$) of $G$ there is at least one path in the family that…

The comprehensive characterization of the structure of complex networks is essential to understand the dynamical processes which guide their evolution. The discovery of the scale-free distribution and the small world property of real…

Computational Physics · Physics 2009-11-13 Paulino R. Villas Boas , Francisco A. Rodrigues , Gonzalo Travieso , Luciano da F. Costa

We determine the tree which maximizes the distance between characteristic set and subtree core over all trees on $n$ vertices. The asymptotic nature of this distance is also discussed. The problem of extremizing the distance between…

Combinatorics · Mathematics 2020-04-07 Dinesh Pandey , Kamal Lochan Patra

We generalize the results from [X.-D. Zhang, X.-P. Lv, Y.-H. Chen, \textit{Ordering trees by the Laplacian coefficients}, Linear Algebra Appl. (2009), doi:10.1016/j.laa.2009.04.018] on the partial ordering of trees with given diameter. For…

Combinatorics · Mathematics 2015-03-19 Aleksandar Ili\' c

The Wiener index of a graph is the sum of the distances between all pairs of vertices, it has been one of the main descriptors that correlate achemical compound's molecular graph with experimentally gathered data regarding the compound's…

Combinatorics · Mathematics 2007-09-12 Hua Wang

We consider chemical graphs that are defined as connected graphs of maximum degree at most 3. We characterize the extremal graphs, meaning those that maximize or minimize 33 degree-based topological indices. This study shows that five graph…

Combinatorics · Mathematics 2025-01-07 Sébastien Bonte , Gauvain Devillez , Valentin Dusollier , Alain Hertz , Hadrien Mélot

Graph burning is motivated by the spread of social influence, and the burning number measures the speed of the spread. Given that the smallest burning number among the spanning trees of a graph determines the burning number of a connected…

Combinatorics · Mathematics 2025-07-01 Eugene Jun Tong Leong , Kai An Sim , Wen Chean Teh

This is a survey article on trees, with a modest number of proofs to give a flavor of the way these topologies can be efficiently handled. Trees are defined in set-theorist fashion as partially ordered sets in which the elements below each…

General Topology · Mathematics 2007-05-23 Peter J. Nyikos

We give a characterization of the strong degrees of categoricity of computable structures greater or equal to $\mathbf 0''$. They are precisely the \emph{treeable} degrees -- the least degrees of paths through computable trees -- that…

Logic · Mathematics 2023-05-12 Barbara F. Csima , Dino Rossegger

While the notion of arboricity of a graph is well-known in graph theory, very few results are dedicated to the minimal number of trees covering the edges of a graph, called the tree number of a graph.

Discrete Mathematics · Computer Science 2020-08-03 Natalia Vanetik

In a connected graph G, the distance between two vertices of G is the length of a shortest path between these vertices. The eccentricity of a vertex u in G is the largest distance between u and any other vertex of G. The total-eccentricity…

Combinatorics · Mathematics 2017-11-21 Rashid Farooq , Mehar Ali Malik , Juan Rada

Sparse trees are trees with sparse branchings. The Laplacian on some of these trees can be shown to have singular spectral measures. We focus on a simple family of sparse trees for which the dimensions can be naturally defined and shown to…

Spectral Theory · Mathematics 2007-05-23 Jonathan Breuer

Let $T$ be a tree with a given adjacency eigenvalue $\lambda$. In this paper, by using the $\lambda$-minimal trees, we determine the structure of trees with a given multiplicity of the eigenvalue $\lambda$. Furthermore, we consider the…

Combinatorics · Mathematics 2021-01-05 Asghar Bahmani , Dariush Kiani

The eccentricity of a vertex $v$ in a graph $G$ is the maximum distance from $v$ to any other vertex. The vertices whose eccentricity are equal to the diameter (the maximum eccentricity) of $G$ are called peripheral vertices. In trees the…

Combinatorics · Mathematics 2019-09-02 Ya-Hong Chen , Hua Wang , Xiao-Dong Zhang

A caterpillar tree is a connected, acyclic, graph in which all vertices are either a member of a central path, or joined to that central path by a single edge. In other words, caterpillar trees are the class of trees which become path…

Combinatorics · Mathematics 2018-10-30 Jacob Crabtree

The subgraph number of a vertex in a graph is defined as the number of connected subgraphs containing that vertex. The graph and its vertex which correspond to the minimum subgraph number among all graphs on $n$ vertices and $k$ cut…

Combinatorics · Mathematics 2025-08-11 Dinesh Pandey , Peruvemba Sundaram Ravi

This study explores the irregularity properties of trees with prescribed degree sequences by analyzing two prominent topological indices: the Albertson index and the sigma index. With a particular emphasis on caterpillar trees -frequently…

Combinatorics · Mathematics 2025-12-16 Jasem Hamoud , Alexey Belov Yakovlevich , Muaadh Almahalebi , Duaa Abdullah