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Research interests

My main area of research is in group theory. I am interested in simple groups, both finite and algebraic, with a particular focus on subgroup structure, conjugacy classes and representation theory. I am also interested in permutation groups and related combinatorics, and in the application of probabilistic and computational methods.

In March 2021 I gave a series of online lectures on Bases for permutation groups, hosted by the University of Padova.

I am a member of the editorial board of the Journal of Algebra. I also served on the editorial board of the Journal of Group Theory (2015-2025), as editor, managing editor and co-editor-in-chief.

Publication highlights

I have written over 70 research publications, which have attracted more than 800 citations according to MathSciNet. This includes three books and monographs, as well as papers in several leading journals:
  • Advances in Mathematics (5 papers)

  • Algebra and Number Theory (2)

  • Annals of Mathematics

  • Journal of the European Mathematical Society (2)

  • Mathematische Annalen

  • Memoirs of the American Mathematical Society (2)

  • Proceedings of the London Mathematical Society (2)

  • Transactions of the American Mathematical Society (2)

Books and monographs



  • Classical groups, derangements and primes
    joint with M. Giudici
    Australian Mathematical Society Lecture Series, vol. 25
    Cambridge University Press, 2016, xviii+346
    ISBN: 978-1-1076-2944-8


  • Irreducible geometric subgroups of classical algebraic groups
    joint with S. Ghandour and D.M. Testerman
    Memoirs of the American Mathematical Society 239 (2016), no. 1130, vi+88
    ISBN: 978-1-4704-1494-8


  • Irreducible almost simple subgroups of classical algebraic groups
    joint with S. Ghandour, C. Marion and D.M. Testerman
    Memoirs of the American Mathematical Society 236 (2015), no. 1114, vi+110
    ISBN: 978-1-4704-1046-9

All publications and preprints

  1. On the intersections of nilpotent subgroups of simple groups
    joint with H.Y. Huang
    37 pages, submitted

  2. On the intersections of Sylow subgroups in almost simple groups
    joint with H.Y. Huang
    26 pages, submitted

  3. On the depth of subgroups of simple groups
    37 pages, submitted

  4. On fixed-point-free involutions in actions of finite exceptional groups of Lie type
    joint with M. Korhonen
    Journal of the London Mathematical Society, to appear

  5. On derangements in simple permutation groups
    joint with M. Fusari
    Forum of Mathematics, Sigma 13 (2025), e98, 62 pp.

  6. On the topological generation of exceptional groups by unipotent elements
    Transformation Groups 30 (2025), 481-520

  7. Topological generation of simple algebraic groups
    joint with S. Gerhardt and R.M. Guralnick
    Journal of the European Mathematical Society (JEMS) 27 (2025), 2865-2951

  8. On the regularity number of a finite group and other base-related invariants
    joint with M. Anagnostopoulou-Merkouri
    Journal of the London Mathematical Society 110 (2024), e70035, 65 pp.
    [Supplementary file]

  9. On the generation of simple groups by Sylow subgroups
    joint with R.M. Guralnick
    Contemporary Mathematics (Amitsur Centennial Symposium), vol. 800 (2024), 81-100, Amer. Math. Soc. Providence, RI.

  10. On the maximal overgroups of Sylow subgroups of finite groups
    joint with B. Baumeister, R.M. Guralnick and H.P. Tong-Viet
    Advances in Mathematics 444 (2024), 109632, 65 pp.

  11. Strongly base-two groups
    joint with R.M. Guralnick
    Vietnam Journal of Mathematics (Tiep 60th birthday volume) 51 (2023), 657-683

  12. On the classification of extremely primitive affine groups
    joint with M. Lee
    Israel Journal of Mathematics 255 (2023), 265-282

  13. On the commuting probability of p-elements in a finite group
    joint with R.M. Guralnick, A. Moretó and G. Navarro
    Algebra and Number Theory 17 (2023), 1209-1229

  14. On soluble subgroups of sporadic groups
    Israel Journal of Mathematics 254 (2023), 313-340

  15. Normalisers of maximal tori and a conjecture of Vdovin
    joint with A.R. Thomas
    Journal of Algebra 619 (2023), 459-504

  16. On the soluble graph of a finite group
    joint with A. Lucchini and D. Nemmi
    Journal of Combinatorial Theory, Series A 194 (2023), 105708, 39 pp.

  17. On base sizes for primitive groups of product type
    joint with H.Y. Huang
    Journal of Pure and Applied Algebra 227 (2023), 107228, 43 pp.

  18. Fixed point ratios for finite primitive groups and applications
    joint with R.M. Guralnick
    Advances in Mathematics 411 (2022), 108778, 90 pp.

  19. On the Saxl graphs of primitive groups with soluble stabilisers
    joint with H.Y. Huang
    Algebraic Combinatorics 5 (2022), 1053-1087

  20. The classification of extremely primitive groups
    joint with A.R. Thomas
    International Mathematics Research Notices IMRN (2022), no. 13, 10148-10248
    [GAP and Magma code]

  21. Finite groups, minimal bases and the intersection number
    joint with M. Garonzi and A. Lucchini
    Transactions of the London Mathematical Society 9 (2022), 20-55

  22. Permutation groups with restricted stabilizers
    joint with A. Shalev
    Journal of Algebra (special issue in memory of Jan Saxl) 607 (2022), 160-185

  23. Almost elusive permutation groups
    joint with E.V. Hall
    Journal of Algebra 594 (2022), 519-543

  24. Base sizes for primitive groups with soluble stabilisers
    Algebra and Number Theory 15 (2021), 1755-1807

  25. On the involution fixity of simple groups
    joint with E. Covato
    Proceedings of the Edinburgh Mathematical Society 64 (2021), 408-426

  26. The spread of a finite group
    joint with R.M. Guralnick and S. Harper
    Annals of Mathematics 193 (2021), 619-687

  27. A note on extremely primitive affine groups
    joint with A.R. Thomas
    Archiv der Mathematik 116 (2021), 141-152

  28. On solvable factors of almost simple groups
    joint with C.H. Li
    Advances in Mathematics 377 (2021), 107499, 36 pp.

  29. Finite groups, 2-generation and the uniform domination number
    joint with S. Harper
    Israel Journal of Mathematics 239 (2020), 271-367

  30. Topological generation of exceptional algebraic groups
    joint with S. Gerhardt and R.M. Guralnick
    Advances in Mathematics 369 (2020), 107177, 50 pp.

  31. On the minimal dimension of a finite simple group
    joint with M. Garonzi and A. Lucchini (with an appendix by T.C. Burness and R.M. Guralnick)
    Journal of Combinatorial Theory, Series A 171 (2020), 105175, 32 pp.

  32. The length and depth of compact Lie groups
    joint with M.W. Liebeck and A. Shalev
    Mathematische Zeitschrift 294 (2020), 1457-1476

  33. On the Saxl graph of a permutation group
    joint with M. Giudici
    Mathematical Proceedings of the Cambridge Philosophical Society 168 (2020), 219-248

  34. On the length and depth of finite groups
    joint with M.W. Liebeck and A. Shalev (with an appendix by D.R. Heath-Brown)
    Proceedings of the London Mathematical Society 119 (2019), 1464-1492

  35. Simple groups, generation and probabilistic methods
    Groups St Andrews 2017 in Birmingham, London Mathematical Society Lecture Note Series, 455, Cambridge University Press, pp. 200-229, 2019

  36. Irreducible subgroups of simple algebraic groups - a survey
    joint with D.M. Testerman
    Groups St Andrews 2017 in Birmingham, London Mathematical Society Lecture Note Series, 455, Cambridge University Press, pp. 230-260, 2019

  37. $A_1$-type subgroups containing regular unipotent elements
    joint with D.M. Testerman
    Forum of Mathematics, Sigma 7 (2019), e12, 61 pp.

  38. On the uniform domination number of a finite simple group
    joint with S. Harper
    Transactions of the American Mathematical Society 372 (2019), 545-583
    [GAP and Magma code]

  39. The length and depth of algebraic groups
    joint with M.W. Liebeck and A. Shalev
    Mathematische Zeitschrift 291 (2019), 741-760

  40. On base sizes for almost simple primitive groups
    Journal of Algebra 516 (2018), 38-74

  41. On the involution fixity of exceptional groups of Lie type
    joint with A.R. Thomas
    International Journal of Algebra and Computation 28 (2018), 411-466

  42. Locally elusive classical groups
    joint with M. Giudici
    Israel Journal of Mathematics 225 (2018), 343-402

  43. Simple groups, fixed point ratios and applications
    Local Representation Theory and Simple Groups, EMS Series of Lectures in Mathematics, European Mathematical Society, Zürich, pp. 267-322, 2018

  44. The depth of a finite simple group
    joint with M.W. Liebeck and A. Shalev
    Proceedings of the American Mathematical Society 146 (2018), 2343-2358

  45. Generation of second maximal subgroups and the existence of special primes
    joint with M.W. Liebeck and A. Shalev
    Forum of Mathematics, Sigma 5 (2017), e25, 41 pp.

  46. On base sizes for algebraic groups
    joint with R.M. Guralnick and J. Saxl
    Journal of the European Mathematical Society (JEMS) 19 (2017), 2269-2341

  47. Permutation groups and derangements of odd prime order
    joint with M. Giudici
    Journal of Combinatorial Theory, Series A 151 (2017), 102-130

  48. On irreducible subgroups of simple algebraic groups
    joint with C. Marion and D.M. Testerman
    Mathematische Annalen 367 (2017), 1259-1309

  49. Primitive permutation groups and derangements of prime power order
    joint with H.P. Tong-Viet
    Manuscripta Mathematica 150 (2016), 255-291

  50. Classical groups, derangements and primes
    joint with M. Giudici
    Australian Mathematical Society Lecture Series, vol. 25
    Cambridge University Press, 2016, xviii+346

  51. Irreducible geometric subgroups of classical algebraic groups
    joint with S. Ghandour and D.M. Testerman
    Memoirs of the American Mathematical Society 239 (2016), no. 1130, vi+88

  52. On Pyber's base size conjecture
    joint with Á. Seress
    Transactions of the American Mathematical Society 367 (2015), 5633-5651

  53. Derangements in primitive permutation groups, with an application to character theory
    joint with H.P. Tong-Viet
    Quarterly Journal of Mathematics 66 (2015), 63-96

  54. On the prime graph of simple groups
    joint with E. Covato
    Bulletin of the Australian Mathematical Society 91 (2015), 227-240

  55. Large subgroups of simple groups
    joint with S.H. Alavi
    Journal of Algebra (special issue in memory of Ákos Seress) 421 (2015), 187-233

  56. Irreducible almost simple subgroups of classical algebraic groups
    joint with S. Ghandour, C. Marion and D.M. Testerman
    Memoirs of the American Mathematical Society 236 (2015), no. 1114, vi+110

  57. Base sizes for $\mathcal{S}$-actions of finite classical groups
    joint with R.M. Guralnick and J. Saxl
    Israel Journal of Mathematics 199 (2014), 711-756

  58. Generation and random generation: from simple groups to maximal subgroups
    joint with M.W. Liebeck and A. Shalev
    Advances in Mathematics 248 (2013), 59-95

  59. On the generating graph of direct powers of a simple group
    joint with E. Crestani
    Journal of Algebraic Combinatorics 38 (2013), 329-350

  60. On the uniform spread of almost simple linear groups
    joint with S. Guest
    Nagoya Mathematical Journal 209 (2013), 35-109

  61. Extremely primitive sporadic and alternating groups
    joint with C.E. Praeger and Á. Seress
    Bulletin of the London Mathematical Society 44 (2012), 1147-1154

  62. Extremely primitive classical groups
    joint with C.E. Praeger and Á. Seress
    Journal of Pure and Applied Algebra 216 (2012), 1580-1610

  63. Prime order derangements in primitive permutation groups
    joint with M. Giudici and R.A. Wilson
    Journal of Algebra 341 (2011), 158-178

  64. On base sizes for symmetric groups
    joint with R.M. Guralnick and J. Saxl
    Bulletin of the London Mathematical Society 43 (2011), 386-391

  65. Base sizes for sporadic simple groups
    joint with E.A. O'Brien and R.A. Wilson
    Israel Journal of Mathematics 177 (2010), 307-334

  66. On the number of prime order subgroups of finite groups
    joint with S.D. Scott
    Journal of the Australian Mathematical Society 87 (2009), 329-357

  67. Base sizes for simple groups and a conjecture of Cameron
    joint with M.W. Liebeck and A. Shalev
    Proceedings of the London Mathematical Society 97 (2009), 116-162

  68. On base sizes for actions of finite classical groups
    Journal of the London Mathematical Society 75 (2007), 545-562

  69. Fixed point ratios in actions of finite classical groups, IV
    Journal of Algebra 314 (2007), 749-788

  70. Fixed point ratios in actions of finite classical groups, III
    Journal of Algebra 314 (2007), 693-748

  71. Fixed point ratios in actions of finite classical groups, II
    Journal of Algebra 309 (2007), 80-138

  72. Fixed point ratios in actions of finite classical groups, I
    Journal of Algebra 309 (2007), 69-79

  73. Fixed point spaces in actions of classical algebraic groups
    Journal of Group Theory 7 (2004), 311-346

  74. Fixed point spaces in primitive actions of simple algebraic groups
    Journal of Algebra 265 (2003), 744-771

Theses

  1. Fixed point spaces in actions of finite and algebraic simple groups
    Ph.D. thesis, Imperial College London (2005)

  2. Reductive algebraic groups and Tits systems
    M.Sc. thesis, University of Warwick (2001)