A general VDB topological index of $ G $ is defined as
$ \mathcal{TI}_f(G) = \sum\limits_{v_iv_j\in E(G)} f(d_i,d_j), $
where $ f(d_i, d_j) $ is a symmetric function, and $ d_i $ represents the degree of $ v_i\in V(G) $. This paper aims to address the maximum chemical tree problem for general vertex-degree-based topological indices with given number of pendant vertices via a unified method. Sufficient conditions for general VDB topological indices to take their maximum value are presented, and as an application, we show that there are six VDB topological indices, including the reciprocal sum-connectivity index, the Sombor index, and the Euler Sombor index, etc., that satisfy these conditions.
Citation: Zhenhua Su. Maximizing chemical trees of some vertex-degree-based topological indices with given number of pendant vertices[J]. AIMS Mathematics, 2025, 10(9): 21240-21253. doi: 10.3934/math.2025948
A general VDB topological index of $ G $ is defined as
$ \mathcal{TI}_f(G) = \sum\limits_{v_iv_j\in E(G)} f(d_i,d_j), $
where $ f(d_i, d_j) $ is a symmetric function, and $ d_i $ represents the degree of $ v_i\in V(G) $. This paper aims to address the maximum chemical tree problem for general vertex-degree-based topological indices with given number of pendant vertices via a unified method. Sufficient conditions for general VDB topological indices to take their maximum value are presented, and as an application, we show that there are six VDB topological indices, including the reciprocal sum-connectivity index, the Sombor index, and the Euler Sombor index, etc., that satisfy these conditions.
| [1] |
H. Wiener, Structural determination of paraffin boiling points, J. Am. Chem. Soc., 69 (1947), 17–20. http://dx.doi.org/10.1021/ja01193a005 doi: 10.1021/ja01193a005
|
| [2] | R. Todeschini, V. Consonni, Handbook of molecular descriptors, Weinheim: Wiley-VCH, 2000. https://dx.doi.org/10.1002/9783527613106 |
| [3] |
P. Nithya, S. Elumalai, Smallest ABS index of unicyclic graphs with given girth, J. Appl. Math. Comput., 69 (2023), 3675–3692. http://dx.doi.org/10.1007/s12190-023-01898-0 doi: 10.1007/s12190-023-01898-0
|
| [4] |
X. Chen, General sum-connectivity index of a graph and its line graph, Appl. Math. Comput., 443 (2023), 127779. http://dx.doi.org/10.1016/j.amc.2022.127779 doi: 10.1016/j.amc.2022.127779
|
| [5] |
M. A. Henning, J. Pardey, D. Rautenbach, F. Werner, Mostar index and bounded maximum degree, Discrete Optim., 54 (2024), 100861. http://dx.doi.org/10.1016/j.disopt.2024.100861 doi: 10.1016/j.disopt.2024.100861
|
| [6] |
Z. Tang, Y. Li, H. Deng, The Euler Sombor index of a graph, Int. J. Quantum Chem., 124 (2024), e27387. http://dx.doi.org/10.1002/qua.27387 doi: 10.1002/qua.27387
|
| [7] |
A. M. Albalahi, A. Ali, A. M. Alanazi, A. A. Bhatti, A. E. Hamza, Harmonic-arithmetic index of (molecular) trees, Contrib. Math., 7 (2023), 41–47. http://dx.doi.org/10.47443/cm.2023.008 doi: 10.47443/cm.2023.008
|
| [8] | I. Gutman, Geometric approach to degree-based topological indices: Sombor indices, MATCH Commun. Math. Comput. Chem., 86 (2021), 11–16. |
| [9] |
V. Maitreyi, S. Elumalai, S. Balachandran, H. Liu, The minimum Sombor index of trees with given number of pendant vertices, Comput. Appl. Math., 42 (2023), 331. http://dx.doi.org/10.1007/s40314-023-02479-4 doi: 10.1007/s40314-023-02479-4
|
| [10] |
H. Liu, H. Chen, Q. Xiao, X. Fang, Z. Tang, More on Sombor indices of chemical graphs and their applications to the boiling point of benzenoid hydrocarbons, Int. J. Quant. Chem., 121 (2021), e26689. http://dx.doi.org/10.1002/qua.26689 doi: 10.1002/qua.26689
|
| [11] |
H. Chen, W. Li, J. Wang, Extremal values on the Sombor index of trees, MATCH Commun. Math. Comput. Chem., 87 (2022), 23–49. http://dx.doi.org/10.46793/match.87-1.023C doi: 10.46793/match.87-1.023C
|
| [12] |
M. Chen, Y. Zhu, Extremal unicyclic graphs of Sombor index, Appl. Math. Comput., 463 (2024), 128374. http://dx.doi.org/10.1016/j.amc.2023.128374 doi: 10.1016/j.amc.2023.128374
|
| [13] |
R. Cruz, J. Rada, Extremal values of the Sombor index in unicyclic and bicyclic graphs, J. Math. Chem., 59 (2021), 1098–1116. http://dx.doi.org/10.1007/s10910-021-01232-8 doi: 10.1007/s10910-021-01232-8
|
| [14] |
K. C. Das, Open problems on Sombor index of unicyclic and bicyclic graphs, Appl. Math. Comput., 473 (2024), 128647. http://dx.doi.org/10.1016/j.amc.2024.128647 doi: 10.1016/j.amc.2024.128647
|
| [15] |
H. Liu, L. You, Y. Huang, Ordering chemical graphs by Sombor indices and its applications, MATCH Commun. Math. Comput. Chem., 87 (2022), 5–22. http://dx.doi.org/10.46793/match.87-1.005L doi: 10.46793/match.87-1.005L
|
| [16] |
A. E. Hamza, Z. Raza, A. Ali, Z. Alsheekhhussain, On Sombor indices of tricyclic graphs, MATCH Commun. Math. Comput. Chem., 90 (2023), 223–234. http://dx.doi.org/10.46793/match.90-1.223h doi: 10.46793/match.90-1.223h
|
| [17] |
I. Redžepović, Chemical applicability of Sombor indices, J. Serb. Chem. Soc., 86 (2021), 445–457. http://dx.doi.org/10.2298/JSC201215006R doi: 10.2298/JSC201215006R
|
| [18] |
Z. Du, L. You, H. Liu, F. Huang, The Sombor index and coindex of chemical graphs, Polycycl. Aromat. Comp., 44 (2024), 2942–2965. https://doi.org/10.1080/10406638.2023.2225683 doi: 10.1080/10406638.2023.2225683
|
| [19] |
H. Liu, L. You, Y. Huang, X. Fang, Spectral properties of p-Sombor matrices and beyond, MATCH Commun. Math. Comput. Chem., 87 (2022), 59–87. http://dx.doi.org/10.46793/match.87-1.059l doi: 10.46793/match.87-1.059l
|
| [20] |
I. Gutman, Relating sombor and Euler indices, Vojnoteh. Glas., 72 (2024), 1–12. http://dx.doi.org/10.5937/vojtehg72-48818 doi: 10.5937/vojtehg72-48818
|
| [21] | X. Hu, L. Zhong, On the general Sombor index of connected unicyclic graphs with given diameter, 2022. https://doi.org/10.48550/arXiv.2208.00418 |
| [22] |
V. Maitreyi, S. Elumalai, B. Selvaraj, On the extremal general Sombor index of trees with given pendent vertices, MATCH Commun. Math. Comput. Chem., 92 (2024), 225–248. http://dx.doi.org/10.46793/match.92-1.225M doi: 10.46793/match.92-1.225M
|
| [23] |
S. Ahmad, K. C. Das, A complete solution for maximizing the general Sombor index of chemical trees with given number of pendant vertices, Appl. Math. Comput., 505 (2025), 129532. http://dx.doi.org/10.1016/j.amc.2025.129532 doi: 10.1016/j.amc.2025.129532
|
| [24] |
S. Brezovnik, N. Tratnik, General cut method for computing Szeged-like topological indices with applications to molecular graphs, Int. J. Quantum Chem., 121 (2021), e26530. http://dx.doi.org/10.1002/qua.26530 doi: 10.1002/qua.26530
|
| [25] |
W. Gao, Extremal graphs with respect to vertex-degree-based topological indices for $c$-cyclic graphs, MATCH Commun. Math. Comput. Chem., 93 (2025), 549–566. http://dx.doi.org/10.46793/match.93-2.549G doi: 10.46793/match.93-2.549G
|
| [26] |
Q. Cui, L. Zhong, On the general sum-connectivity index of trees with given number of pendent vertices, Discrete Appl. Math., 222 (2017), 213–221. http://dx.doi.org/10.1016/j.dam.2017.01.016 doi: 10.1016/j.dam.2017.01.016
|