Abstract
Let V be a vector space of dimension n+1 over a field of p t elements. A d-dimensional subspace and an e-dimensional subspace are considered to be incident if their intersection is not the zero subspace. The rank of these incidence matrices, modulo p, are computed for all n, d, e and t. This result generalizes the well-known formula of Hamada for the incidence matrices between points and subspaces of given dimensions in a finite projective space. A generating function for these ranks as t varies, keeping n, d and e fixed, is also given. In the special case where the dimensions are complementary, i.e., d+e=n+ 1, our formula improves previous upper bounds on the size of partial m-systems (as defined by Shult and Thas).
Similar content being viewed by others
References
E. F. Assmus, Jr. and J. D. Key, Designs and Their Codes, Tracts in Mathematics, Vol. 102, Cambridge University Press, Cambridge, England (1992).
M. Bardoe and P. Sin, The permutation module for GL(n+1,F q acting on ℙn(F q ) and F n+1 q , J. London. Math. Soc., Vol. 61 (2000) pp. 58–80.
N. Hamada, The rank of the incidence matrix of points and d-flats in finite geometries, J. Sci. Hiroshima Univ. Ser., A-I, Vol. 32 (1968) pp. 381–396.
N. Hamilton and R. Mathon, Existence and non-existence of m-systems of polar spaces, Europ. J. Combinatorics, Vol. 22 (2001) pp. 51–61.
E. E. Shult and J. A. Thas, m-systems of polar spaces, J. Combinatorial Theory Ser. A, Vol. 68 (1994) pp. 184–204.
E. E. Shult and J. A. Thas, m-systems and partial m-systems of polar spaces, Designs, Codes and Cryptography, Vol. 8 (1996) pp. 229–238.
R. P. Stanley, Enumerative Combinatorics, Studies in Advanced Mathematics, Vol. 49, Cambridge University Press, Cambridge, England (1992).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Sin, P. The p-Rank of the Incidence Matrix of Intersecting Linear Subspaces. Designs, Codes and Cryptography 31, 213–220 (2004). https://doi.org/10.1023/B:DESI.0000015884.34185.4a
Issue Date:
DOI: https://doi.org/10.1023/B:DESI.0000015884.34185.4a