Maximum Euler Sombor Index of Unicyclic Graphs with Given Diameter

The sum‐connectivity (SC) index of a graph is defined as , where Θ μ denotes the vertex degree of μ in . In this paper, the fourth largest value of SC index for the chemical unicyclic graphs of order n ≥ 7 is determined.

We study the general Randić index of a graph [Formula: see text], [Formula: see text], where [Formula: see text], [Formula: see text] is the edge set of [Formula: see text] and [Formula: see text] and [Formula: see text] are the degrees of vertices [Formula: see text] and [Formula: see text], respectively. For [Formula: see text], we present lower bounds on the general Randić index for unicyclic graphs of given diameter and girth, and unicyclic graphs of given diameter. Lower bounds on the classical Randić index and the second modified Zagreb index are corollaries of our results on the general Randić index.

Chemical graph theory has an important role in the development of chemical sciences. A graph is produced from certain molecular structure by means of applying several graphical operations. The local graph parameter is valency, which is defined for every vertex as the number associates with other vertices in a graph, for example an atom in a molecule. The demonstration of chemical networks and chemical compounds with the help of M-polynomials is a novel idea. The M-polynomial of different molecular structures help to compute several topological indices. A topological index is a numeric quantity that describes the whole structure of a molecular graph of the chemical compound and clarifies its physical features, chemical reactivates and boiling activities. In this paper we computed M-Polynomial and topological indices of TUHRC4 Graph, then we recovered numerous topological indices using the M-polynomials.

The vertex PI index and Szeged index are distance-based topological index which reflect certain structural features of organic molecules. Each structural feature of such organic molecule can be expressed as a graph. In this paper, we determine the vertex PI index and Szeged index of fan molecular graph, wheel molecular graph, gear fan molecular graph, gear wheel molecular graph, and their r-corona molecular graphs.

Introduction: Chemical Graph Theory or CGT for short, is a transdisciplinary field of Mathematics wherein graphs are used to represent chemical compounds. Under this representation, the atoms of a chemical compound are expressed as vertices, while the bonds connecting these atoms are expressed as edges. Once the graph representation of a chemical compound has been determined, graph-theoretic techniques can now be used to determine various topological indices associated with the chemical compound. Topological indices are invariants of a graph that have predictive power for the chemical properties of a chemical compound. In CGT, trees, being connected and acyclic, have been an essential class of graphs. This is because, most compounds have acyclic molecular structures. In the 2023 study by Gowtham and Husin, various reverse topological indices of a family of trees called bistar graphs have been determined. Objectives: Motivated by the work of Gowtham and Husin, we determine some reverse topological indices of another family of trees called comets and double comets. Double comets are natural extension of bistar graphs. We also give a certain computational application of our results on double comet graphs. Finally, we investigate the relationship between the reverse topological indices of bistar graphs and double comets. Methods: Several important graph-theoretic concepts were used to analyze some important properties of comets and double comets, leading to the computation of their reverse vertex degree based topological indices. Results: The following reverse vertex degree-based topological indices for comets and double comets were determined: Reverse sum-connectivity, First reverse Zagreb, Second reverse Zagreb, Reverse arithmetic-geometric, Reverse geometric-arithmetic, Reverse Sombor, and Reverse Nirmala. A computational application of the results to a certain chemical compound (2,2,4,4-Tetramethylpentane) or C9H20 were also demonstrated. Conclusions: The results of the paper provided an extension to an existing result on the reverse vertex degree-based topological indices of bistar graphs by considering double comet graphs. Several topological reverse vertex degree-based topological indices were also computed for comet graphs. The computed topological indices were also applied in determining some invariants of a certain chemical compound. For future studies, we recommend that reverse vertex degree based topological indices of other family of trees will be considered.

A general VDB topological index of G is defined aswhere f (x, y) is a real symmetric function for x 1 and y 1.Recently, Liu et al. (2024) presented a uniform method for solving the extremal problem with general VDB topological indices for ccyclic graphs, which was later extended by Gao (2025) and Ali et al. (2025).In this note, we further investigate this problem.A new mathematical formula for T I f was obtained, which provided sufficient conditions for G to take its minimum value.As an application, we show that there are sixteen VDB topological indices that satisfy these conditions.In addition, we ordered six VDB topological indices for bicyclic and tricyclic graphs.

Very recently, a novel bond‐additive topological descriptor named as the Mostar index has been proposed as a measure of peripherality in networks and graphs. In this article, we compute the Mostar index of generalized Hierarchical product, lexicographic product, Cartesian product, corona product, join, subdivision vertex‐edge join and Indu–Bala products of graphs and apply these results to determine the Mostar index of some types of nanostructures and chemical graphs. As an application, we give the explicit expressions for the Mostar index of various nanostructures and chemical graphs.

The Fibonacci index of a graph is the number of its stable sets. This parameter is widely studied and has applications in chemical graph theory. In this paper, we establish tight upper bounds for the Fibonacci index in terms of the stability number and the order of general graphs and connected graphs. Turán graphs frequently appear in extremal graph theory. We show that Turán graphs and a connected variant of them are also extremal for these particular problems. We also make a polyhedral study by establishing all the optimal linear inequalities for the stability number and the Fibonacci index, inside the classes of general and connected graphs of order n.

Let be a simple connected graph with vertex set and edge set . The Randić index of graph is the value , where and refer to the degree of the vertices and . We obtain a lower bound for the Randić index of trees in terms of the order and the Roman domination number, and we characterize the extremal trees for this bound.

A Topological index is a molecular structure descriptor of a molecular graph and it has many applications in real world issues. The Zagreb Indices based on degree of vertices of a graph are widely studied in chemical graph theory in over the past few years. Degree based Zagreb indices of undirected graphs {G_{m,n}}^M and G_n graphs are computed in this paper.

In the performance characterization of chemical molecular structures, several uncertain properties are often encountered, and fuzzy theory is precisely the tool to characterize these uncertainties. When molecular structures are described by molecular graphs, the corresponding fuzzy graph theory is used to characterize the uncertainty of atoms and atomic bonds. In this study, there is introduced cyclic connectivity index and its average version for bipolar fuzzy incidence graph (BFIG), and several theoretical results are obtained in the light of graph theory and fuzzy theory. Finally, the given new fuzzy index is applied to the testing of anti-aging-related drugs yields average uncertainty data for the corresponding molecular structures.

The Wiener index is a topological index of a molecular graph, defined as the sum of distances between all pairs of its vertices. Benzenoid graphs include molecular graphs of polycyclic aromatic hydrocarbons. An edge thorny graph G is constructed from a catacondensed benzenoid graph H by attaching new graphs to edges of a perfect matching of H. A formula for the Wiener index of G is derived. The index of the resulting graph does not contain distance characteristics of elements of H and depends on the Wiener index of H and distance properties of the attached graphs.

A graph in which atoms are taken as vertices and bonds can be shown by edges is called a molecular graph. For such graphs we can find the indices showing their bioactivity as well as their physio-chemical properties. Industry is flourishing nowadays just because of the interdisciplinary study of different subjects. This gives us a way to understand the application of different subjects. Chemical graph theory is a mixture of chemistry and mathematics both play an important role in chemical graph theory. Chemistry provides a chemical compound and graph theory transform this chemical compound into a molecular graph which further studied by different aspects such as topological indices. In this article, we computed generalized Randić, general Zagreb, general sum-connectivity, ABC, GA, and indices of line graphs of the and nanotubes.”

The aim of this paper is to present exact formulas for the vertex and edge PI indices of the generalized hierarchical product of graphs. As a consequence of our results, these indices were computed for some chemical graphs.

In mathematical chemistry topological index is a type of molecular descriptor that is computed based on chemical graph of chemical compound. In chemical graph atoms and bond corresponds to vertices and edges. In this paper we compute harmonic index and harmonic polynomial for silicon carbide graphs for the list of silicon carbide graphs.