The modular Weyl–Kac character formula

Christopher Bowman*, Amit Hazi, Emily Norton

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We classify and explicitly construct the irreducible graded representations of anti-spherical Hecke categories which are concentrated one degree. Each of these homogeneous representations is one-dimensional and can be cohomologically constructed via a BGG resolution involving every (infinite dimensional) standard representation of the category. We hence determine the complete first row of the inverse parabolic p-Kazhdan–Lusztig matrix for an arbitrary Coxeter group and an arbitrary parabolic subgroup. This generalises the Weyl–Kac character formula to all Coxeter systems (and their parabolics) and proves that this generalised formula is rigid with respect to base change to fields of arbitrary characteristic.

Original languageEnglish
Number of pages26
JournalMathematische Zeitschrift
Publication statusPublished - 23 Sept 2022

Bibliographical note

Funding Information:
We would like to thank George Lusztig and Stephen Donkin for their helpful comments. We would also like to thank the anonymous referees for their detailed reading of the paper and their helpful suggestions. The authors are grateful for funding from EPSRC grant EP/V00090X/1, the Royal Commission for the Exhibition of 1851, and European Research Council grant No. 677147, respectively.

Publisher Copyright:
© 2022, The Author(s).


  • Hecke categories
  • p-Kazhdan-Lusztig polynomials
  • Weyl-Kac character formula

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