Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10118382 | European Journal of Combinatorics | 2005 | 9 Pages |
Abstract
Let Î denote a near polygon distance-regular graph with diameter dâ¥3, valency k and intersection numbers a1>0, c2>1. Let θ1 denote the second largest eigenvalue of Î. We showθ1â¤kâa1âc2c2â1.We show the following (i)-(iii) are equivalent. (i) Equality is attained above; (ii) Î is Q-polynomial with respect to θ1; (iii) Î is a dual polar graph or a Hamming graph.
Related Topics
Physical Sciences and Engineering
Mathematics
Discrete Mathematics and Combinatorics
Authors
Paul Terwilliger, Chih-wen Weng,