Jan Draisma

Professor of Mathematics

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3 November 2025: Schläfli lecture by Kathlén Kohn.

Teaching

Linear and Bilinear Algebra

This site contains information about the course Linear and Bilinear Algebra. The first half of the course we will use lecture notes by Arjeh Cohen, the following 30 percent we will treat material a book by Babai and Frankl about linear algebra methods in combinatorics, and the last 20 percent is devoted to other fun applications. To get credit points you need to hand in homework every week and, at the end, to write a text about one of the later chapters, or about an article. So far we have done:
  • Week 1 (31 August and 1 September): Chapter 1 of lecture notes. Homework: Exercise 1.7 + Find an invertible 2-by-2 matrix over Z/13Z of order 7.
  • Week 2 (7 and 8 September): Chapter 2, sections 1 and 2. eomework: Exercise 2.5 and the exercise in this document, which also gives a clean definition of extension of scalars.
  • Week 3 (14 and 15 September): Chapter 2, sections 3 and 4. Homework: Exercise 2.9 and this extra exercise.
  • Week 4 (21 and 22 September): Chapter 2, rational Jordan normal form. Homework: Exercise 2.19 and this extra exercise.
  • Week 7 (12 and 13 October): Tensor products, Kronecker products, etc. Homework: Excercise 3.11.
  • Week 8 (19 and 20 October): Tensor rank. Homework: this exercise.
  • Week 9 (9 and 10 November): Bilinear forms. Homework: these exercises.
  • Week 10 (16 and 17 November): Sesquilinear forms. Homework: these exercises.
  • Week 11 (23 and 24 November): Orthogonal, symplectic, unitary groups; exterior powers of spaces and of maps. Homework: these exercises.
  • Week 12 (30 November and 1 December): Bollobás's theorem with Lovász's proof.
  • Week 13 (7 and 8 December): Perron-Frobenius. Homework: these exercises.
  • Week 14 (4 and 5 January): Two linear algebra proofs in combinatorics. Homework: this exercise.