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On the Strongly Regular Unit Distance Graphs

Bhaskar Bagchi1, Pratima Panigrahi2, Uma kant Sahoo 2
1Statistics and Mathematics Unit, Indian Statistical Institute, Bangalore 560 059, INDIA
2Department of Mathematics, Indian Institute of Technology, Kharagpur 721 302, INDIA

Abstract

A unit distance graph is a finite simple graph which may be drawn on the plane so that its vertices are represented by distinct points and the edges are represented by closed line segments of unit length. In this paper, we show that the only primitive strongly regular unit distance graphs are \((i)\) the pentagon, \((ii)\) \(K_3 \times K_3\), \((iii)\) the Petersen graph, and \((iv)\) possibly the Hoffman-Singleton graph.

Keywords: The unit distance graph, euclidean distance, Moore graphs, three dimensional hypercube, strongly regular graphs