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The geometric girth of a distance-regular graph having certain thin irreducible modules for the Terwilliger algebra
- Source :
-
European Journal of Combinatorics . Feb2006, Vol. 27 Issue 2, p235-254. 20p. - Publication Year :
- 2006
-
Abstract
- Abstract: Let be a distance-regular graph of diameter . Suppose that does not have any induced subgraph isomorphic to . In this case, the length of a shortest reduced circuit in is called the geometric girth of . Except for ordinary polygons, all known examples have a property that in general, and if . Is there an absolute constant bound on the geometric girth of a distance-regular graph with valency at least three? This is one of the main problems in the field of distance-regular graphs. P. Terwilliger defined an algebra with respect to a base vertex , which is called a subconstituent algebra or a Terwilliger algebra. The investigation of irreducible -modules and their thin property proved to be a very important tool to study structures of distance-regular graphs. B. Collins proved that if every irreducible -module is thin then is at most 8, and if , then and is a generalized octagon. In this paper, we prove the same result under an assumption that every irreducible -module of endpoint at most 3 is thin. [Copyright &y& Elsevier]
- Subjects :
- *MATHEMATICS
*ALGEBRA
*MATHEMATICAL analysis
*GRAPHIC methods
Subjects
Details
- Language :
- English
- ISSN :
- 01956698
- Volume :
- 27
- Issue :
- 2
- Database :
- Academic Search Index
- Journal :
- European Journal of Combinatorics
- Publication Type :
- Academic Journal
- Accession number :
- 19334692
- Full Text :
- https://doi.org/10.1016/j.ejc.2004.08.006