© The London Mathematical Society
The Action of Finite Orthogonal Groups in Characteristic 2 on the Set of Anisotropic Lines
Combinatorial and Computational Mathematics Center, Pohang University of Science and Technology San 31 Hyoja-dong, Nam-Gu, Pohang 790-784, Korea fujisaki{at}postech.ac.kr
Received 5 February 2003. Revision received 6 October 2004.
We prove that the permutation representation of the finite orthogonal group 
(n,q), where
= + or , on the set of anisotropic lines is multiplicity-free, if q is a power of 2 and n
6 is even. This result is established by giving a description of orbitals of this action. The rank of this action is (q2 + 2q)/2 if
= + and n = 6, and (q2 + 2q + 2)/2 otherwise. Moreover, we compute the subdegrees of the orbitals of 
(n,q).