On the graphs of a fixed cyclomatic number and order with minimum general sum-connectivity and Platt indices

被引:2
作者
Albalahi, Abeer M. [1 ]
Du, Zhibin [2 ]
Ali, Akbar [1 ]
Alanazi, Abdulaziz M. [3 ,4 ,5 ]
机构
[1] Univ Hail, Coll Sci, Dept Math, Hail, Saudi Arabia
[2] South China Normal Univ, Sch Software, Foshan, Peoples R China
[3] Univ Tabuk, Dept Math, Tabuk 71491, Saudi Arabia
[4] Georgia Southern Univ, Dept Math Sci, Statesboro, Georgia
[5] Georgia Southern Univ, Dept Math Sci, Savannah, GA USA
关键词
Cyclomatic number; Topological index; General Platt index; General sum-connectivity index; EXTREMAL GRAPHS; CHI(ALPHA);
D O I
10.1007/s40314-024-02647-0
中图分类号
O29 [应用数学];
学科分类号
070104 ;
摘要
The general sum-connectivity and Platt indices of a graph G are defined by SCa(G)= n-ary sumation xy is an element of E(G)(dx+dy)a\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text {SC}}_a(G)=\sum _{xy\in E(G)}(d_x+d_y)<^>a$$\end{document} and Pla(G)= n-ary sumation xy is an element of E(G)(dx+dy-2)a\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text {Pl}}_a(G)=\sum _{xy\in E(G)}(d_x+d_y-2)<^>a$$\end{document}, respectively, where a is a real number, E(G) indicates the edge set of G, and dv\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$d_v$$\end{document} indicates the degree of a vertex v of G. The cyclomatic number of G is the least number of edges required to be deleted from G to make it acyclic. If the maximum degree of G is less than 5, then G is referred to as a molecular graph. In this paper, the problem of determining graphs possessing the minimum values of the indices SCa\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text {SC}}_a$$\end{document} and Pla\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text {Pl}}_a$$\end{document} among all connected (molecular) graphs of order n and cyclomatic number t is solved for 0<a<1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$0<a<1$$\end{document} and n >= 2(t-1)>= 2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$n\ge 2(t-1)\ge 2$$\end{document} with n >= 4\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$n\ge 4$$\end{document}. It is proved that the difference between the maximum and minimum degrees of the aforementioned extremal graphs is at most 1.
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