Abstract
The bilinear forms graph denoted here by Bilq(d×e) is a graph defined on the set of (d×e)-matrices (e≥d) over \(\mathbb{F}_q\) with two matrices being adjacent if and only if the rank of their difference equals 1.
In 1999, K. Metsch showed that the bilinear forms graph Bilq(d×e), d≥3, is characterized by its intersection array if one of the following holds:
— q=2 and e≥d+4
— q≥3 and e≥d+3.
Thus, the following cases have been left unsettled:
— q=2 and e∈{d,d+1,d+2,d+3}
— q≥3 and e∈{d,d+1,d+2}.
In this work, we show that the graph of bilinear (d×d)-forms over the binary field, where d≥3, is characterized by its intersection array. In doing so, we also classify locally grid graphs whose μ-graphs are hexagons and their intersection numbers bi,ci are well-defined for all i=0,1,2.
Similar content being viewed by others
References
E. Bannai and T. Ito: Algebraic combinatorics. I. Association schemes, The Benjamin/Cummings Publishing Co., Inc., Menlo Park, CA, 1984. xxiv+425.
S. Bang, T. Fujisaki and J. H. Koolen: The spectra of the local graphs of the twisted Grassmann graphs, European J. Combin. 30 (2009), 638–654.
A. Blokhuis and A. E. Brouwer: Locally 4-by-4 grid graphs, J. Graph Theory 13 (1989), 229–244.
A. E. Brouwer, A. M. Cohen and A. Neumaier: Distance-regular graphs, Ergebnisse der Mathematik und ihrer Grenzgebiete, (3), 18. Springer-Verlag, Berlin, 1989. xviii+495 pp.
A. E. Brouwer and W. H. Haemers: Spectra of Graphs, Springer, Heidelberg, 2012.
P. Cameron: Strongly regular graphs, in: Selected Topics in Algebraic Graph Theory (eds. L. W. Beineke and R. J. Wilson), Cambridge Univ. Press, 2004.
K. Coolsaet and A. Jurišić: Using equality in the Krein conditions to prove nonexistence of certain distance-regular graphs, J. Combin. Theory Ser. A 115 (2008), 1086–1095.
H. Cuypers: Two remarks on Huang's characterization of the bilinear forms graphs, Europ. J. Combinatorics 13 (1992), 33–37.
H. Cuypers: The dual of Pasch's axiom, Europ. J. Combinatorics 13 (1992), 15–31.
E. Van Dam: Regular graphs with four eigenvalues, Linear Algebra Appl. 226–228 (1995), 139–162.
E. Van Dam, J. H. Koolen and H. Tanaka: Distance-regular graphs, Electronic Journal of Combinatorics, Dynamic Survey DS22.
I. Debroey: Semi partial geometries satisfying the diagonal axiom, J. of Geometry 13 (1979), 171–190.
T.-S. Fu and T. Huang: A Unified Approach to a Characterization of Grassmann Graphs and Bilinear Forms Graphs, Europ. J. Combinatorics 15 (1994), 363–373.
A. L. Gavrilyuk and J. H. Koolen: The Terwilliger polynomial of a Q-polynomial distance-regular graph and its application to pseudo-partition graphs, Linear Algebra Appl. 466 (2015), 117–140.
C. Godsil and G. Royle: Algebraic Graph Theory, Springer-Verlag, New York, Berlin, Heidelberg, 2001.
S. Hobart and T. Ito: The structure of nonthin irreducible T-modules of endpoint 1: ladder bases and classical parameters, J. Algebraic Combin. 7 (1998), 53–75.
T. Huang: A characterization of the association schemes of bilinear forms, Europ. J. Combinatorics 8 (1987), 159–173.
A. Jurišić and J. Vidali: Extremal 1-codes in distance-regular graphs of diameter 3, Des. Codes Cryptogr., 65 (2012), 29–47.
A. A. Makhnev and D. V. Paduchikh: Characterization of graphs of alternating and quadratic forms as covers of locally Grassman graphs, Doklady Mathematics 79 (2009), 158–162.
K. Metsch: Improvement of Bruck's completion theorem, Des. Codes Cryptogr. 1 (1991), 99–116.
K. Metsch: On a Characterization of Bilinear Forms Graphs, Europ. J. Combinatorics 20 (1999), 293–306.
A. Munemasa and S. V. Shpectorov: A local characterization of the graph of alternating forms, in: Finite Geometry and Combinatorics (Ed. F. de Clerck and J. Hirschfeld.), Cambridge Univ. Press, 289–302, 1993.
A. Munemasa, D. V. Pasechnik and S. V. Shpectorov: A local characterization of the graphs of alternating forms and the graphs of quadratic forms over GF(2), in: Finite Geometry and Combinatorics (Ed. F. de Clerck and J. Hirschfeld.), Cambridge Univ. Press, 303–318, 1993.
S. S. Shrikhande: The uniqueness of the L 2 association scheme, Ann. Math. Statist. 30 (1959), 781–798.
A. Sprague: Incidence structures whose planes are nets, Europ. J. Combinatorics 2 (1981), 193–204.
P. Terwilliger: Lecture note on Terwilliger algebra (edited by H. Suzuki), 1993.
P. Terwilliger: The subconstituent algebra of an association scheme, I, J. Algebraic Combin. 1 (1992), 363–388.
M. Urlep: Triple intersection numbers of Q-polynomial distance-regular graphs, European J. Combin. 33 (2012), 1246–1252.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Gavrilyuk, A.L., Koolen, J.H. A Characterization of the Graphs of Bilinear (d×d)-Forms over \(\mathbb{F}_2\). Combinatorica 39, 289–321 (2019). https://doi.org/10.1007/s00493-017-3573-4
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00493-017-3573-4