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Title:
Geometric Approach to Degree-Based Topological Indices: Degree-Ratio Sombor Indices of Graphs
Authors:
Gasper George Nyauli ORCID iD 0009-0003-5962-0618
Jibonjyoti Buragohain ORCID iD 0000-0002-6421-9920
Volume
97
Issue
1
Year
2027
Pages
135-164
Abstract

An alternative geometric interpretation of vertex-degree-based topological indices is introduced. Let \( \left(d(u), d(v)\right) \) denote the degree pair of the edge \( uv \in E(G) \) and \( \left(\frac{d(u)}{d(v)}, \frac{d(v)}{d(u)}\right) \) its corresponding degree-ratio pair. Based on the Euclidean metric, a novel class of graph invariants is considered, of which the simplest member is a Degree-Ratio Sombor index DRSO. The DRSO index is obtained by summing the terms \( \sqrt{ \Big(\frac{d(u)}{d(v)}\Big)^{2} + \Big(\frac{d(v)}{d(u)}\Big)^{2} } \) over all edges \( uv\in E(G) \). Fundamental mathematical properties of the DRSO index are established. Several structural variants of the DRSO index, including the modified and reduced versions, are formulated.