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In this paper, we presents novel and sharp bounds on the Albertson index of trees, revealing deep connections between degree sequences and graph irregularity where the Albertson index of Caterpillar tree satisfy \[…

General Mathematics · Mathematics 2025-12-16 Jasem Hamoud , Duaa Abdullah

We establish sharp extremal bounds on the Albertson and Sigma irregularity indices for trees with prescribed degree sequences, with emphasis on caterpillar trees as key extremal configurations. New lower and upper bounds are derived in…

Combinatorics · Mathematics 2026-03-12 Jasem Hamoud , Duaa Abdullah

In this paper, we presented a study of topological indices on trees, where we show a relationship with irregularity of Albertson index and minimum, maximum degrees $\delta,\Delta$ of graph $G$, where contribute vital roles in determining…

Combinatorics · Mathematics 2025-11-26 Jasem Hamoud , Artem Kornosov

In this paper, we have studied bounds based on topological indicators, from which we selected Albertson index $\mathrm{irr}$ and the Sigma index $\sigma$. The Sigma index was defined through the following relationship: \[…

Combinatorics · Mathematics 2025-06-16 Jasem Hamoud , Alexei Belov-Kanel , Duaa Abdullah

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

In this paper, we establishe the extremal bounds of the topological indices -- Sigma index -- focusing on analyzing the sharp upper bounds and the lower bounds of the Sigma index, which is known $\sigma(G)=\sum_{uv\in…

Combinatorics · Mathematics 2026-03-31 Jasem Hamoud , Duaa Abdullah

In this paper, we provide the irregularity properties of trees with strong support vertex by analyzing two prominent topological indices: the Albertson index and the Sigma index. We further establish extremal bounds for both indices across…

Combinatorics · Mathematics 2025-05-13 Jasem Hamoud , Duaa Abdullah

The $\sigma$-irregularity index of a graph is defined as the sum of squared degree differences over all edges and provides a sensitive measure of structural heterogeneity. In this paper, we study the problem of maximizing $\sigma(T)$ among…

Combinatorics · Mathematics 2026-02-17 Milan Bašić

We estimate the maximum ratio between the $\sigma_t$- and $\sigma$-irregularity for graphs and trees of order $n$, which are respectively bounded by $\Theta(n^{5/2})$ and $n-2$. This answers a question and a conjecture by Filipovski et al.…

Combinatorics · Mathematics 2026-04-29 Stijn Cambie , Jionghua Chang

In this paper, we refer to a asymptotic degree sequence as $\mathscr{D}=(d_1,d_2,\dots,d_n)$. The examination of topological indices on trees gives us a general overview through bounds to find the maximum and minimum bounds which reflect…

Combinatorics · Mathematics 2025-12-16 Jasem Hamoud , Duaa Abdullah

The sigma-irregularity index $\sigma(G) = \sum_{uv \in E(G)} (d_G(u) - d_G(v))^2$ measures the total degree imbalance along the edges of a graph. We study extremal problems for $\sigma(T)$ within the class of trees of fixed order $n$ and…

Combinatorics · Mathematics 2026-02-03 Milan Bašić

Albertson defined the irregularity of a graph $G$ as $irr(G)=\sum\limits_{uv\in E(G)}|d_G(u)-d_G(v)|$. For a graph $G$ with $n$ vertices, $m$ edges, maximum degree $\Delta$, and $d=\left\lfloor \frac{\Delta m}{\Delta n-m}\right\rfloor$, we…

Combinatorics · Mathematics 2023-03-23 Dieter Rautenbach , Florian Werner

The degree-based entropy of a graph is defined as the Shannon entropy based on the information functional that associates the vertices of the graph with the corresponding degrees. In this paper, we study extremal problems of finding the…

Combinatorics · Mathematics 2021-09-01 Yanni Dong , Maximilien Gadouleau , Pengfei Wan , Shenggui Zhang

We characterize the bipartite graphs that minimize the (first-degree based) entropy, among all bipartite graphs of given size, or given size and (upper bound on the) order. The extremal graphs turn out to be complete bipartite graphs, or…

Combinatorics · Mathematics 2022-06-03 Stijn Cambie , Yanni Dong , Matteo Mazzamurro

In this paper, degree-based topological indices play a key role in the structural analysis of graphs in this paper and have significant uses in chemical graph theory. We investigate the connections between three such tree indices: the…

Combinatorics · Mathematics 2026-03-10 Duaa Abdullah , Jasem Hamoud

In this paper, we investigate The relationship between the Albertson index and the first Zagreb index for trees. For a tree $T=(V,E)$ with $n=|V|$ vertices and $m=|E|$ edges, we provide several bounds and exact formulas for these two…

Combinatorics · Mathematics 2025-06-03 Jasem Hamoud , Alexei Belov-Kanel , Duaa Abdullah

Albertson has defined the irregularity of a simple undirected graph $G=(V,E)$ as $ \irr(G) = \sum_{uv\in E}|d_G(u)-d_G(v)|,$ where $d_G(u)$ denotes the degree of a vertex $u \in V$. Recently, this graph invariant gained interest in the…

Discrete Mathematics · Computer Science 2015-03-20 Hosam Abdo , Nathann Cohen , Darko Dimitrov

We introduce the general Albertson irregularity index of a connected graph $G$ and define it as $A_{p}(G) =(\sum_{uv\in E(G)}|d(u)-d(v)|^p)^{\frac{1}{p}}$, where $p$ is a positive real number and $d(v)$ is the degree of the vertex $v$ in…

Combinatorics · Mathematics 2021-08-02 Zhen Lin , Ting Zhou , Lianying Miao

In this paper we give new bounds for a several vertex-based and edge-based topological indices of graphs: Albertson irregularity index, degree variance index, Mostar and the first Zagreb index. Moreover, we give a new upper bound for the…

Combinatorics · Mathematics 2022-10-25 Arber Avdullahu , Slobodan Filipovski

Recently, Ali et al. posed several open problems concerning extremal graphs with respect to the ABS index. These problems involve characterizing graphs that attain the maximum ABS index within specific graph classes, including: connected…

Combinatorics · Mathematics 2025-12-30 Swathi Shetty , B. R. Rakshith , Sayinath Udupa N.
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