Olivier Dudas

I am a Directeur de Recherche (Senior Research Fellow) at the CNRS. I recently moved to the Aix-Marseille University and the Institut de Mathématiques de Marseille - (I2M).

You can find me here:

Institut de Mathématiques de Marseille - I2M
Campus de Luminy
Avenue de Luminy
Case 930
13288 Marseille Cedex 9
Office: A203

But the best way to contact me is by email: ["firstname.surname"][at]univ-amu.fr

News and schedule

Je suis responsable d'un comité de sélection pour un poste de MCF à l'I2M, pensez à candidater !

J'ai donné un cours de l'ED d'introduction à la théorie de Deligne--Lusztig. Les notes se trouvent ici (attention, beaucoup de coquilles encore !)

July 7-11, 2024: I will give a talk at the workshop on Diagrammatic Intuition and Deep Learning in Mathematics in York, UK.
May 28, 2024: I will give a seminar talk in Reims.


  1. Rationality of extended unipotent characters, preprint, 2024 (with G. Malle).
  2. Decomposition numbers for unipotent blocks with small sl2-weight in finite classical groups, preprint, 2023 (with E. Norton).
  3. Orthogonality relations for deep level Deligne--Lusztig schemes of Coxeter type, preprint, 2020 (with A. Ivanov).

Published or accepted papers

  1. Decomposition matrices for groups of Lie type in non-defining characteristic, to appear in the Memoirs of the AMS, 2023 (with G. Malle).
  2. Decomposition numbers for the principal Φ2n-block of Sp4n(q) and SO4n+1(q), accepted in Annales de l'Institut Fourier, 2022 (with E. Norton).
  3. The Ext-algebra of the Brauer tree algebra associated to a line, accepted in Revista de la Unión Matemática Argentina, 2021.
  4. Unitriangular shape of decomposition matrices of unipotent blocks, accepted in Ann. of Math., 2020 (with O. Brunat and J. Taylor).
  5. Translation by the full twist and Deligne--Lusztig varieties, J. Algebra 558 (2020), 129--145. (with C. Bonnafé and R. Rouquier).
  6. Categorical actions on unipotent representations of finite unitary groups, Publications Mathématiques de l'IHES 129 (2019), 129--197. (with M. Varagnolo and É. Vasserot).
  7. Non-uniqueness of supercuspidal support for finite reductive groups. Appendix to the article Simple subquotients of big parabolically induced representations of p-adic groups by J.-F. Dat, J. Algebra 510 (2018), 508--512.
  8. Bounding Harish-Chandra series, Transactions of the AMS 371 (2019), 6511--6530.(with G. Malle).
  9. Brauer trees of unipotent blocks, JEMS 22 (2020), no. 9, 2821--2877. (with D. Craven and R. Rouquier).
  10. Alvis-Curtis duality for finite general linear groups and a generalized Mullineux involution, SIGMA 14 (2018) (with N. Jacon).
  11. Lectures on modular Deligne-Lusztig theory, in Local representation theory and simple groups, 107--177, EMS Ser. Lect. Math., Eur. Math. Soc., Zürich, 2018.
  12. Splendeur des variétés de Deligne-Lusztig, d'après Deligne-Lusztig, Broué, Rickard, Bonnafé-Dat-Rouquier, Séminaire Bourbaki, Exp. 1137, to appear in Astérisque, 2017. [You can watch the talk here]
  13. Modular irreducibility of cuspidal unipotent characters, Invent. Math. 211 (2018), 579--589 (with G. Malle).
  14. Categorical actions from Lusztig induction and restriction on finite general linear groups in Representation theory - current trends and perspectives, 59--74, EMS Ser. Congr. Rep., Eur. Math. Soc., Zürich, 2017 (with M. Varagnolo and É. Vasserot).
  15. Categorical actions on unipotent representations of finite classical groups in Categorification and higher representation theory, 41--104, Contemp. Math. (683), Amer. Math. Soc., Providence, RI, 2017 (with M. Varagnolo and É. Vasserot).
  16. Decomposition matrices for exceptional groups at d=4, J. Pure Appl. Algebra 220 (2016), 1096--1121 (with G. Malle).
  17. Decomposition matrices for low rank unitary groups, Proc. London Math. Soc. 110 (2015), 1517--1557 (with G. Malle).
  18. Projective modules in the intersection cohomology of Deligne--Lusztig varieties, C. R. Acad. Sci. (2014), 467--471. (with G. Malle). [I gave a talk about this here]
  19. Cohomology of Deligne-Lusztig varieties for unipotent blocks of GLn(q), Represent. Th. 17 (2013), 647--662.
  20. A note on decomposition numbers for groups of Lie type of small rank , J. Algebra 388 (2013), 364--373.
  21. Coxeter orbits and Brauer trees III, J. Amer. Math. Soc. 27 (2014), 1117--1145 (with R. Rouquier).
  22. Cohomology of Deligne-Lusztig varieties for short-length regular elements in exceptional groups, J. Algebra 392 (2013), 276--298.
  23. Quotient of Deligne-Lusztig varieties, J. Algebra 381 (2013), 1--20.
  24. Coxeter orbits and Brauer trees II, Int. Math. Res. Not. 15 (2014), 4100--4123.
  25. Coxeter orbits and Brauer trees, Adv. Math. 229 (2012), 3398--3435.
  26. Deligne-Lusztig restriction of a Gelfand-Graev module, Ann. Sci. Ec. Norm. Sup. 42 (2009), 653--674.


Categorical actions on unipotent representations of finite unitary groups, Oberwolfach report, Group theory, 2015.
Quotients of Deligne-Lusztig varieties, Oberwolfach report, Group theory, 2012.
Geometry of Deligne-Lusztig varieties, decompositions, mod \ell cohomology and modular representations, PhD thesis, 2010.
Note on the Deodhar decomposition, preprint.

Some (rather old) talks

I rarely use beamer for giving talks so this is pretty old material:

A talk about the joint work [9] with Gunter Malle.
Brauer trees of finite reductive groups via Deligne-Lusztig theory, Pohang, March 2011.
Some Slides I used during my viva, Besançon, June 2010.
Parity sheaves (with Peng Shan), Sheaves in representation theory, Isle of Skye, May 2010.
Autour des représentations linéaires des groupes finis classiques, Journées des écoles doctorales de Besançon et Dijon, Dijon, May 09.