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Qiao, Zhi; Koolen, Jack
Journal of combinatorial theory. Series B, March 2019, 2019-03-00, Volume: 135Journal Article
In this paper we give a new characterization of the dual polar graphs, extending the work of Brouwer and Wilbrink on regular near polygons. Also as a consequence of our characterization we confirm a conjecture of the authors on non-bipartite distance-regular graphs with smallest eigenvalue at most −k/2, where k is the valency of the distance-regular graph, in the case where c2≥3 and a1=1.
