All Stories

  1. A spectral characterization of the s-clique extension of the triangular graphs

    Article • Discussiones Mathematicae Graph Theory, January 2020, Faculty of Mathematics, Computer Science and Econometrics, University of Zielona Gora

    Jack Koolen

  2. Another construction of edge-regular graphs with regular cliques

    Article • Discrete Mathematics, October 2019, Elsevier

    Jack Koolen

  3. Distance-regular graphs without 4-claws

    Article • European Journal of Combinatorics, August 2019, Elsevier

    Jack Koolen

  4. On 2-walk-regular graphs with a large intersection number c2

    Article • European Journal of Combinatorics, August 2019, Elsevier

    Jack Koolen

  5. A generalization of a theorem of Hoffman

    Article • Journal of Combinatorial Theory Series B, March 2019, Elsevier

    Jack Koolen

  6. A new characterization of the dual polar graphs

    Article • Journal of Combinatorial Theory Series B, March 2019, Elsevier

    Jack Koolen

  7. The polytopal structure of the tight-span of a totally split-decomposable metric

    Article • Discrete Mathematics, March 2019, Elsevier

    Jack Koolen

  8. A spectral characterization of the s-clique extension of the square grid graphs

    Article • European Journal of Combinatorics, February 2019, Elsevier

    Jack Koolen

  9. Addressing Johnson Graphs, Complete Multipartite Graphs, Odd Cycles, and Random Graphs

    Article • Experimental Mathematics, January 2019, Taylor & Francis

    Sebastian Cioaba, Jack Koolen

  10. On graphs with smallest eigenvalue at least −3 and their lattices

    Article • Advances in Mathematics, November 2018, Elsevier

    Jack Koolen

  11. A Characterization of the Graphs of Bilinear (d×d)-Forms over $$\mathbb{F}_2$$

    Article • COMBINATORICA, August 2018, Springer Science + Business Media

    Jack Koolen

  12. On fat Hoffman graphs with smallest eigenvalue at least −3, part II

    Article • Linear Algebra and its Applications, August 2018, Elsevier

    Jack Koolen

  13. The spectral excess theorem for graphs with few eigenvalues whose distance-2 or distance-1-or-2 graph is strongly regular

    Article • Linear and Multilinear Algebra, July 2018, Taylor & Francis

    Jack Koolen

  14. Edge-regular graphs with regular cliques

    Article • European Journal of Combinatorics, June 2018, Elsevier

    Jack Koolen

  15. Partially metric association schemes with a multiplicity three

    Article • Journal of Combinatorial Theory Series B, May 2018, Elsevier

    Jack Koolen

  16. A valency bound for distance-regular graphs

    Article • Journal of Combinatorial Theory Series A, April 2018, Elsevier

    Jack Koolen

  17. Graphs with three eigenvalues and second largest eigenvalue at most 1

    Article • Journal of Combinatorial Theory Series B, March 2018, Elsevier

    Jack Koolen

  18. Distance-regular graphs of diameter 3 having eigenvalue −1

    Article • Linear Algebra and its Applications, October 2017, Elsevier

    Jack Koolen

  19. Max-cut and extendability of matchings in distance-regular graphs

    Article • European Journal of Combinatorics, May 2017, Elsevier

    Jack Koolen

  20. Graphs with two main and two plain eigenvalues

    Article • Applicable Analysis and Discrete Mathematics, January 2017, National Library of Serbia

    Jack Koolen

  21. A note on graphs with exactly two main eigenvalues

    Article • Linear Algebra and its Applications, December 2016, Elsevier

    Jack Koolen

  22. 2-Walk-regular graphs with a small number of vertices compared to the valency

    Article • Linear Algebra and its Applications, December 2016, Elsevier

    Jack Koolen

  23. Preface to the special issue dedicated to Andries E. Brouwer

    Article • Designs Codes and Cryptography, November 2016, Springer Science + Business Media

    Jack Koolen

  24. Corrigendum to “Hypercubes are determined by their distance spectra” [Linear Algebra Appl. 505 (2016) 97–108]

    Article • Linear Algebra and its Applications, October 2016, Elsevier

    Jack Koolen

  25. A structure theory for graphs with fixed smallest eigenvalue

    Article • Linear Algebra and its Applications, September 2016, Elsevier

    Jack Koolen

  26. Hypercubes are determined by their distance spectra

    Article • Linear Algebra and its Applications, September 2016, Elsevier

    Jack Koolen

  27. Biregular graphs with three eigenvalues

    Article • European Journal of Combinatorics, August 2016, Elsevier

    Jack Koolen

  28. A generalization of a theorem of Neumaier

    Article • Designs Codes and Cryptography, June 2016, Springer Science + Business Media

    Jack Koolen

  29. Light tails and the Hermitian dual polar graphs

    Article • Designs Codes and Cryptography, March 2016, Springer Science + Business Media

    Jack Koolen

  30. Equiangular lines in Euclidean spaces

    Article • Journal of Combinatorial Theory Series A, February 2016, Elsevier

    Jack Koolen

  31. A collection of results concerning electric resistance and simple random walk on distance-regular graphs

    Article • Discrete Mathematics, February 2016, Elsevier

    Jack Koolen

  32. Maximizing the Order of a Regular Graph of Given Valency and Second Eigenvalue

    Article • SIAM Journal on Discrete Mathematics, January 2016, Society for Industrial & Applied Mathematics (SIAM)

    Jack Koolen

  33. Some Results on the Eigenvalues of Distance-Regular Graphs

    Article • Graphs and Combinatorics, September 2015, Springer Science + Business Media

    Jack Koolen

  34. Optimal realizations of two-dimensional, totally-decomposable metrics

    Article • Discrete Mathematics, August 2015, Elsevier

    Jack Koolen

  35. Graphs with many valencies and few eigenvalues

    Article • Electronic Journal of Linear Algebra, April 2015, University of Wyoming Libraries

    Jack Koolen

  36. The Terwilliger polynomial of a Q-polynomial distance-regular graph and its application to pseudo-partition graphs

    Article • Linear Algebra and its Applications, February 2015, Elsevier

    Jack Koolen

  37. Edge-signed graphs with smallest eigenvalue greater than −2

    Article • Journal of Combinatorial Theory Series B, January 2015, Elsevier

    Jack Koolen

  38. There are only finitely many distance-regular graphs of fixed valency greater than two

    Article • Advances in Mathematics, January 2015, Elsevier

    Jack Koolen

  39. Twice Q-polynomial distance-regular graphs of diameter 4

    Article • Science in China Series A Mathematics, December 2014, Springer Science + Business Media

    Jack Koolen

  40. Regular graphs with maximal energy per vertex

    Article • Journal of Combinatorial Theory Series B, July 2014, Elsevier

    Jack Koolen

  41. Disconnecting strongly regular graphs

    Article • European Journal of Combinatorics, May 2014, Elsevier

    Jack Koolen

  42. On geometric distance-regular graphs with diameter three

    Article • European Journal of Combinatorics, February 2014, Elsevier

    Jack Koolen

  43. Geometric aspects of 2-walk-regular graphs

    Article • Linear Algebra and its Applications, November 2013, Elsevier

    Jack Koolen

  44. There are only finitely many distance-regular graphs with valency k at least three, fixed ratiok2kand large diameter

    Article • Journal of Combinatorial Theory Series B, November 2013, Elsevier

    Jack Koolen

  45. A note on distance-regular graphs with a small number of vertices compared to the valency

    Article • European Journal of Combinatorics, August 2013, Elsevier

    Jack Koolen

  46. On electric resistances for distance-regular graphs

    Article • European Journal of Combinatorics, May 2013, Elsevier

    Jack Koolen

  47. On the connectedness of the complement of a ball in distance-regular graphs

    Article • Journal of Algebraic Combinatorics, September 2012, Springer Science + Business Media

    Jack Koolen

  48. Injective optimal realizations of finite metric spaces

    Article • Discrete Mathematics, May 2012, Elsevier

    Jack Koolen

  49. On a conjecture of Brouwer involving the connectivity of strongly regular graphs

    Article • Journal of Combinatorial Theory Series A, May 2012, Elsevier

    Jack Koolen

  50. Distance-regular graphs with

    Article • Journal of Combinatorial Theory Series A, April 2012, Elsevier

    Jack Koolen

  51. The size of 3-compatible, weakly compatible split systems

    Article • Journal of Applied Mathematics and Computing, February 2012, Springer Science + Business Media

    Jack Koolen

  52. A relationship between the diameter and the intersection number c 2 for a distance-regular graph

    Article • Designs Codes and Cryptography, December 2011, Springer Science + Business Media

    Jack Koolen

  53. The distance-regular graphs such that all of its second largest local eigenvalues are at most one

    Article • Linear Algebra and its Applications, November 2011, Elsevier

    Jack Koolen

  54. The non-bipartite integral graphs with spectral radius three

    Article • Linear Algebra and its Applications, November 2011, Elsevier

    Jack Koolen

  55. Core-periphery disparity in fractal behavior of complex networks

    Article • Physical Review E, September 2011, American Physical Society (APS)

    Jack Koolen

  56. An inequality involving the second largest and smallest eigenvalue of a distance-regular graph

    Article • Linear Algebra and its Applications, June 2011, Elsevier

    Jack Koolen

  57. Classification of the family

    Article • Journal of Combinatorial Theory Series A, April 2011, Elsevier

    Jack Koolen

  58. Blocks and Cut Vertices of the Buneman Graph

    Article • SIAM Journal on Discrete Mathematics, January 2011, Society for Industrial & Applied Mathematics (SIAM)

    Jack Koolen

  59. Shilla distance-regular graphs

    Article • European Journal of Combinatorics, December 2010, Elsevier

    Jack Koolen

  60. On distance-regular graphs with smallest eigenvalue at least −m

    Article • Journal of Combinatorial Theory Series B, November 2010, Elsevier

    Jack Koolen

  61. An Algorithm for Computing Cutpoints in Finite Metric Spaces

    Article • Journal of Classification, September 2010, Springer Science + Business Media

    Jack Koolen

  62. A lower bound for the spectral radius of graphs with fixed diameter

    Article • European Journal of Combinatorics, August 2010, Elsevier

    Jack Koolen

  63. A relation between the Laplacian and signless Laplacian eigenvalues of a graph

    Article • Journal of Algebraic Combinatorics, April 2010, Springer Science + Business Media

    Jack Koolen

  64. Delsarte Set Graphs with Small c 2

    Article • Graphs and Combinatorics, February 2010, Springer Science + Business Media

    Jack Koolen

  65. Asymptotic results on the spectral radius and the diameter of graphs

    Article • Linear Algebra and its Applications, January 2010, Elsevier

    Jack Koolen

  66. Quartets in maximal weakly compatible split systems

    Article • Applied Mathematics Letters, October 2009, Elsevier

    Jack Koolen

  67. Optimal realizations of generic five-point metrics

    Article • European Journal of Combinatorics, July 2009, Elsevier

    Jack Koolen

  68. The spectra of the local graphs of the twisted Grassmann graphs

    Article • European Journal of Combinatorics, April 2009, Elsevier

    Jack Koolen

  69. The vertex-connectivity of a distance-regular graph

    Article • European Journal of Combinatorics, April 2009, Elsevier

    Jack Koolen

  70. A graph-theoretical invariant of topological spaces

    Article • Applied Mathematics Letters, February 2009, Elsevier

    Jack Koolen

  71. Basic Phylogenetic Combinatorics

    Article • January 2009, Cambridge University Press

    Jack Koolen

  72. Block realizations of finite metrics and the tight-span construction I: The embedding theorem

    Article • Applied Mathematics Letters, December 2008, Elsevier

    Jack Koolen

  73. Spectral characterization of the Hamming graphs

    Article • Linear Algebra and its Applications, December 2008, Elsevier

    Jack Koolen

  74. Compatible decompositions and block realizations of finite metrics

    Article • European Journal of Combinatorics, October 2008, Elsevier

    Jack Koolen

  75. Characterization of the Patterson graph

    Article • Journal of Algebra, September 2008, Elsevier

    Jack Koolen

  76. On triangle-free distance-regular graphs with an eigenvalue multiplicity equal to the valency

    Article • European Journal of Combinatorics, July 2008, Elsevier

    Jack Koolen

  77. Preface

    Article • Discrete Mathematics, July 2008, Elsevier

    Jack Koolen

  78. Cut points in metric spaces

    Article • Applied Mathematics Letters, June 2008, Elsevier

    Jack Koolen

  79. GRAPHS COSPECTRAL WITH H(3, q) WHICH ARE DISJOINT UNIONS OF AT MOST THREE COMPLETE GRAPHS

    Article • Asian-European Journal of Mathematics, June 2008, World Scientific Pub Co Pte Lt

    Jack Koolen

  80. Triangle-free distance-regular graphs with an eigenvalue multiplicity equal to their valency and diameter 3

    Article • European Journal of Combinatorics, January 2008, Elsevier

    Jack Koolen

  81. Distance-regular graphs with complete multipartite μ-graphs and AT4 family

    Article • Journal of Algebraic Combinatorics, January 2007, Springer Science + Business Media

    Jack Koolen

  82. Combinatorics of lopsided sets

    Article • European Journal of Combinatorics, July 2006, Elsevier

    Jack Koolen

  83. On the structure of the tight-span of a totally split-decomposable metric

    Article • European Journal of Combinatorics, April 2006, Elsevier

    Jack Koolen

  84. Improving diameter bounds for distance-regular graphs

    Article • European Journal of Combinatorics, January 2006, Elsevier

    Jack Koolen

  85. The tight span of an antipodal metric space—Part I:

    Article • Discrete Mathematics, November 2005, Elsevier

    Jack Koolen

  86. Triangle- and pentagon-free distance-regular graphs with an eigenvalue multiplicity equal to the valency

    Article • Journal of Combinatorial Theory Series B, July 2005, Elsevier

    Jack Koolen

  87. Article • Discrete Applied Mathematics, February 2005, Elsevier

    Jack Koolen

  88. 4n�?�10

    Article • Annals of Combinatorics, January 2005, Springer Science + Business Media

    Jack Koolen

  89. A generalization of an inequality of Brouwer–Wilbrink

    Article • Journal of Combinatorial Theory Series A, January 2005, Elsevier

    Jack Koolen

  90. A Note on Regular Near Polygons

    Article • Graphs and Combinatorics, November 2004, Springer Science + Business Media

    Jack Koolen

  91. A Higman-Haemers Inequality for Thick Regular Near Polygons

    Article • Journal of Algebraic Combinatorics, September 2004, Springer Science + Business Media

    Jack Koolen

  92. The Regular Near Polygons of Order (s, 2)

    Article • Journal of Algebraic Combinatorics, September 2004, Springer Science + Business Media

    Jack Koolen

  93. The Tight Span of an Antipodal Metric Space: Part II?Geometrical Properties

    Article • Discrete & Computational Geometry, March 2004, Springer Science + Business Media

    Jack Koolen

  94. There are Finitely Many Triangle-Free Distance-Regular Graphs with Degree 8, 9 or 10

    Article • Journal of Algebraic Combinatorics, March 2004, Springer Science + Business Media

    Jack Koolen

  95. The structure of spherical graphs

    Article • European Journal of Combinatorics, February 2004, Elsevier

    Jack Koolen

  96. A bound for the number of columns ℓ(c,a,b) in the intersection array of a distance-regular graph

    Article • European Journal of Combinatorics, October 2003, Elsevier

    Jack Koolen

  97. Width and dual width of subsets in polynomial association schemes

    Article • Journal of Combinatorial Theory Series A, May 2003, Elsevier

    Jack Koolen

  98. Addendum to “on line arrangements in the hyperbolic plane” [European J. Combin. 23 (2002) 549–557]

    Article • European Journal of Combinatorics, April 2003, Elsevier

    Jack Koolen

  99. A root graph that is locally the line graph of the Petersen graph

    Article • Discrete Mathematics, March 2003, Elsevier

    Jack Koolen

  100. Maximal Energy Bipartite Graphs

    Article • Graphs and Combinatorics, March 2003, Springer Science + Business Media

    Jack Koolen

  101. Article • Journal of Algebraic Combinatorics, January 2003, Springer Science + Business Media

    Jack Koolen

  102. On a Conjecture of Bannai and Ito: There are Finitely Many Distance-regular Graphs with Degree 5, 6 or 7

    Article • European Journal of Combinatorics, November 2002, Elsevier

    Jack Koolen

  103. Hyperbolic Bridged Graphs

    Article • European Journal of Combinatorics, August 2002, Elsevier

    Jack Koolen

  104. On Line Arrangements in the Hyperbolic Plane

    Article • European Journal of Combinatorics, July 2002, Elsevier

    Jack Koolen

  105. Six Points Suffice: How to Check for Metric Consistency

    Article • European Journal of Combinatorics, May 2001, Elsevier

    Jack Koolen

  106. Maximal Energy Graphs

    Article • Advances in Applied Mathematics, January 2001, Elsevier

    Jack Koolen

  107. Nonexistence of some Antipodal Distance-regular Graphs of Diameter Four

    Article • European Journal of Combinatorics, November 2000, Elsevier

    Jack Koolen

  108. A Classification of the Six-point Prime Metrics

    Article • European Journal of Combinatorics, August 2000, Elsevier

    Jack Koolen

  109. Improving the McClelland inequality for total π-electron energy

    Article • Chemical Physics Letters, April 2000, Elsevier

    Jack Koolen

  110. Estimating and Approximating the Total π-Electron Energy of Benzenoid Hydrocarbons

    Article • Zeitschrift für Naturforschung A, January 2000, De Gruyter

    Jack Koolen, Tanja Soldatovic

  111. Article • Journal of Algebraic Combinatorics, January 2000, Springer Science + Business Media

    Jack Koolen

  112. Article • Journal of Algebraic Combinatorics, January 1999, Springer Science + Business Media

    Jack Koolen

  113. The coherency index

    Article • Discrete Mathematics, October 1998, Elsevier

    Jack Koolen

  114. The Distance-regular Graphs with Intersection Number and with an Eigenvalue

    Article • COMBINATORICA, February 1998, Springer Science + Business Media

    Jack Koolen

  115. ON DISTANCE-REGULAR GRAPHS WITH c4=1 AND a1≠a2

    Article • Kyushu Journal of Mathematics, January 1998, Faculty of Mathematics, Kyushu University

    Jack Koolen

  116. Article • Journal of Algebraic Combinatorics, January 1998, Springer Science + Business Media

    Jack Koolen

  117. A Characterization of the Doob Graphs

    Article • Journal of Combinatorial Theory Series B, September 1995, Elsevier

    Jack Koolen

  118. On a conjecture of Martin on the parameters of completely regular codes and the classification of the completely regular codes in the biggs-smith graph

    Article • Linear and Multilinear Algebra, July 1995, Taylor & Francis

    Jack Koolen

  119. Distance-regular Graphs the Distance Matrix of which has Only One Positive Eigenvalue

    Article • European Journal of Combinatorics, May 1994, Elsevier

    Jack Koolen

  120. On uniformly geodetic graphs

    Article • Graphs and Combinatorics, June 1993, Springer Science + Business Media

    Jack Koolen

  121. A new condition for distance-regular graphs

    Article • European Journal of Combinatorics, January 1992, Elsevier

    Jack Koolen