Hyperplanes of $DW(5,{\mathbb{K}})$ with ${\mathbb{K}}$ a perfect field of characteristic 2

  • Authors:
  • Bart Bruyn

  • Affiliations:
  • Department of Pure Mathematics and Computer Algebra, Ghent University, Gent, Belgium 9000

  • Venue:
  • Journal of Algebraic Combinatorics: An International Journal
  • Year:
  • 2009

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Abstract

Let ${\mathbb{K}}$ be a perfect field of characteristic 2. In this paper, we classify all hyperplanes of the symplectic dual polar space $DW(5,{\mathbb{K}})$ that arise from its Grassmann embedding. We show that the number of isomorphism classes of such hyperplanes is equal to 5+N, where N is the number of equivalence classes of the following equivalence relation R on the set $\{\lambda\in {\mathbb{K}}\,|\,X^{2}+\lambda X+1\mbox{ isirreducible}$ $\mbox{in }{\mathbb{K}}[X]\}$ : (驴 1,驴 2)驴R whenever there exists an automorphism 驴 of ${\mathbb{K}}$ and an $a\in {\mathbb{K}}$ such that (驴 2 驴 )驴1=驴 1 驴1 +a 2+a.