Journalartikel

Jahr der Veröffentlichung: 2022

Zeitschrift: Journal of Combinatorial Theory, Series A

Bandnummer: 192

ISSN: 0097-3165

eISSN: 1096-0899

Open Access Status: Green

DOI Link: https://doi.org/10.1016/j.jcta.2022.105657

Verlag: Elsevier

Abstract: 
In this paper, oppositeness in spherical buildings is used to define an EKR-problem for flags in projective and polar spaces. A novel application of the theory of buildings and Iwahori-Hecke algebras is developed to prove sharp upper bounds for EKR-sets of flags. In this framework, we can reprove and generalize previous upper bounds for EKR-problems in projective and polar spaces. The bounds are obtained by the application of the Delsarte-Hoffman coclique bound to the opposition graph. The computation of its eigenvalues is due to earlier work by Andries Brouwer and an explicit algorithm is worked out. For the classical geometries, the execution of this algorithm boils down to elementary combinatorics. Connections to building theory, Iwahori-Hecke algebras, classical groups and diagram geometries are briefly discussed. Several open problems are posed throughout and at the end.(c) 2022 Elsevier Inc. All rights reserved.

Harvard-Zitierstil: De Beule, J., Mattheus, S. and Metsch, K. (2022) An algebraic approach to Erd?s-Ko-Rado sets of flags in spherical buildings, Journal of Combinatorial Theory, Series A, 192, Article 105657. https://doi.org/10.1016/j.jcta.2022.105657

APA-Zitierstil: De Beule, J., Mattheus, S., & Metsch, K. (2022). An algebraic approach to Erd?s-Ko-Rado sets of flags in spherical buildings. Journal of Combinatorial Theory, Series A. 192, Article 105657. https://doi.org/10.1016/j.jcta.2022.105657