Algebraic groups and related topics

LMS/EPSRC short instructional course

Monday 15–Friday 19 September 2008

School of Mathematics

University of Birmingham

Below are provisional synopses for the courses along with some possible prereading. If you have any questions, please email me goodwin(at)maths.bham.ac.uk.
Introduction to algebraic groups

The course will cover the basics of the theory of linear algebraic groups, hopefully ending with an outline of the classification of reductive linear algebraic groups. Topics that are likely to be covered include:

  • Actions and representations of algebraic groups;
  • Jordan decomposition;
  • Lie algebra of an algebraic group;
  • Solvable groups and Borel subgroups;
  • Parabolic subgroups;
  • Maximal tori and root datum;
  • Reductive groups.

Suggested prereading:
Basic knowledge from affine algebraic geometry will be assumed. This can be found in:

  • Reid, Undergraduate algebraic geometry, Chapter II.
  • Geck, An introduction to algebraic geometry and algebraic groups, 1.1–1.3, 2.1.
The material to be covered in the course will mostly be contained in:
  • Geck, An introduction to algebraic geometry and algebraic groups.
  • Humphreys, Linear algebraic groups.
  • Springer, Linear algebraic groups.
Finite groups of Lie type and Hecke algebras

A preliminary synopsis is as follows:

  • Frobenius maps on algebraic groups, examples
  • Harish-Chandra series of representations
  • Hecke algebras
  • Kazhdan-Lusztig basis and cellular structure
  • Examples, open problems

Suggested prereading:
Basic knowledge of representation theory will be assumed, as would be contained in first course. This is covered in for example:

  • James and Liebeck, Representations and Characters of Groups.
  • Serre, Linear Representations of Finite Groups, Chapter 1.
A single reference to give an idea of what will be covered in the course is:
  • Geck, Modular representations of Hecke algebras. http://arxiv.org/abs/math/0511548
    in Group representation theory (EPFL, 2005; eds. M. Geck, D. Testerman and J. Th\'evenaz), pp.~301--353, Presses Polytechniques et Universitaires Romandes, EPFL-Press, Lausanne, 2007.
Prereading for Frobenius morphisms and representations of finite groups of Lie type:
  • Geck, An introduction to algebraic geometry and algebraic groups.
  • Digne and Michel, Representations of Finite Groups of Lie Type.
Prereading for Hecke algebras and cellular structures:
  • Humphreys, Reflection groups and Coxeter groups.
  • Mathas, Iwahori–Hecke algebras and Schur algebras of the symmetric group.
Modular representations of Lie algebras

A provisional synopsis is as follows:

  • Simple Lie algebras over C: roots and Weyl group, Dynkin diagrams; highest weight modules; nilpotent orbits.
  • Reduced enveloping algebras; problem primes; Kac–Weisfeiler Conjecture; Verma modules, simple modules, blocks; special cases.
  • Nilpotent variety: Springer resolution and fibers; BMR theorems; subregular case.
  • Cells in affine Weyl group, Lusztig bijection; examples; dimension formulas?
  • Lusztig’s program: assign modules to left cells? conjectures and examples
Suggested prereading:
Familiarity with Lie algebras, root systems and Weyl groups will be assumed. This material is covered in for example:
  • Erdmann and Wildon, Introduction to Lie algebras.
  • Humphreys, Introduction to Lie algebras and representation theory.
  • Humphreys, Reflection groups and Coxeter groups.
For general information and references on representations of Lie algebras in positive characteristic, see for example
  • Jantzen, Representations of Lie algebras in prime characteristic, in Representation theories and algebraic geometry, Kluwer (1998).
  • Jantzen, Survey on representations of Lie algebras in prime characteristic, available at http://home.imf.au.dk/jantzen/.
For information on nilpotent orbits see
  • Jantzen, Nilpotent orbits in representation theory, in Lie Theory, Progress in Math., vol. 228, Birkh\"auser, 2004.