Math 101 Topics in Algebra: Quadratic Forms

The official syllabus in pdf form.

Syllabus

Updated October 5, 2020.

List of useful texts:

Week Date Topics Reading Homework
1 Mon 14 Sep History of quadratic forms. Bilinear forms.
Wed 16 Sep Quadratic and symmetric bilinear forms. Space of bilinear forms. Radical. Lam I.1-I.2, Kahn 1.1, Scharlau 1.1-1.3
Fri 18 Sep Tensor products. Symmetric squares. Symmetric tensors. Lam I.4, I.6-7, Kahn 1.2, Scharlau 1.5, Math3ma
2 Mon 21 Sep Isometries. Orthogonal group. Orthogonal complements. Lam I.4, I.6-7, Kahn 1.2, Scharlau 1.5
Wed 23 Sep Orthogonal sum. Subform splitting lemma. Lam I.4, I.6-7, Kahn 1.2, Scharlau 1.5
Fri 25 Sep Diagonalization. Representing units. Reflections. Lam I.4, I.6-7, Kahn 1.2, Scharlau 1.5
3 Mon 28 Sep No class: Yom Kippur
Wed 30 Sep Witt cancellation. Isotropy and hyperbolic spaces. Totally isotropic subspaces. Lam I.3-I.4, Kahn 1.2, Scharlau 1.4-1.5
Fri 02 Oct Square classes. Quadratic extensions and étale algebras. Relations on diagonalizations. Lam I.3-I.4, Kahn 1.2, Scharlau 1.4-1.5
4 Mon 05 Oct Sylvester's law of inertia. Quadratic forms over finite fields. Lam II.3, Scharlau 2.3-2.4 Problem Set #1
Wed 07 Oct Binary forms. Witt decomposition. Witt group. Grothendieck-Witt group. Lam II.1, Scharlau 2.1, Kahn 1.3
Fri 09 Oct Tensor product of quadratic forms. Witt ring. Grothendieck-Witt ring. Fundamental ideal. Reduced dimension and signed discriminant. Fundamental filtration. Milnor conjecture. Lam V.1-V.3, Scharlau 8.3, Kahn 6.2
5 Mon 12 Oct Unital algebras. Tensor algebra. Graded rings and homogeneous ideals. Clifford algebra. Lam V.1-V.3, Scharlau 8.3, Kahn 6.2
Wed 14 Oct Even Clifford algebra. Tensor product of algebras. Graded tensor product of Z/2Z-algebras. Clifford algebra of an orthogonal sum. Lam V.1-V.3, Scharlau 8.3, Kahn 6.2
Fri 16 Oct Center of Clifford algebra. Central simple algebras. Lam V.1-V.3, Scharlau 8.3, Kahn 6.2
6 Mon 19 Oct Division algebras. Artin-Wedderburn. Splitting of central simple algebras. Brauer equivalence. Brauer group. Problem Set #2
Wed 21 Oct Quaternion algebras. Biquaternion algebras. Albert form. Merkurjev's theorem the 2-torsion of the Brauer group. A peek at cyclic algebras and Merkurjev-Suslin. Clifford invariant and Hasse-Witt invariant.
Fri 23 Oct Elementary invariants. Fundamental filtration of the Witt group.
7 Mon 26 Oct Discrete valuations. Laurent series fields. Order of vanishing on rational function fields. Ostrowski's theorem for rational function fields. Lam VI.1, Sharlau Ch. 3 Appendix, Dummit-Foote 16.2
Wed 28 Oct Discrete valuation rings. p-adic valuation. Absolute values. Ostrowski's theorem. Ostrowski's theorem Q and F(t)
Fri 30 Oct Metric topology induced by a valuation. Completions. Inverse limits. Lam VI.1, Sharlau Ch. 3 Appendix, Dummit-Foote 16.2
8 Mon 02 Nov More completions. Hensel's Lemma. Serre II.1
Wed 04 Nov Hensel's Lemma. Square classes in complete discrete valuation fields. Serre II.3.3
Fri 06 Nov Newton's Method and Strong Hensel's Lemma. Multivariable Hensel's Lemma. Serre II.2
9 Mon 09 Nov No class: BATMOBYLE
Wed 11 Nov Springer's theorem for complete discretely valued fields. Residue maps on the Witt group. u-invariant. Tsen's theorem and Tsen-Lang theory. Classification of unimodular quadratic forms over complete DVRs. Lam VI.1, Sharlau 6.2
Fri 13 Nov Local fields. Brauer group of local fields. Classification of quadratic forms over local fields. Lam VI.2, Scharlau 5.6, Serre IV.2
10 Mon 16 Nov Quadratic forms over global fields. Milnor exact sequence. Hasse-Minkowski theorem. Lam VI.3, Scharlau 5.7, Serre IV.3 Final Exam



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