Math 4140/5140
Abstract Algebra II


Spring 2021


Please see below for lecture summaries, homework and other study material.

Date Topics
Jan.15. Review: groups, rings, fields and vector spaces. Notes.
Jan.18. MLK Holiday; no class.
Jan.20. Linear algebra review. Free vector spaces via universal property. Notes. Homework (tex).
Jan.22. More on universal properties. Definition and first example of algebras. Notes.
Jan.25. Polynomial and endomorphism algebras. Notes.
Jan.27. Monoid algebras. Free algebras. Path algebras of quivers. Notes. Homework (tex).
Jan.29. Examples of path algebras. Ideals of algebras. Notes.
Feb.01. Quotient algebras. The first isomorphism theorem for algebras. Notes.
Feb.03. Facts about k[x]. Definition and examples of modules. Notes. Homework (tex).
Feb.05. Submodules. Simplicity of column modules. Quotients modules. Notes.
Feb.08. "Induced" modules. Direct products. External and internal direct sums. Notes.
Feb.10. More on module homomorphisms and isomorphisms. Notes. Homework (tex).
Feb.12. Representations. "Representations are the same as modules". Modules of k[x]. Notes.
Feb.15. More on modules of k[x] and its quotients. Notes.
Feb.17. Wellness Day; no class. Homework (tex).
Feb.19. Modules from group actions. Simple modules. Notes.
Feb.22. Simple vs. cyclic modules. Simpleness of quotient modules. Composition series. Notes.
Feb.24. More examples of composition series. Existence and uniqueness of composition series. Notes. Homework (tex).
Feb.26. Proof of the Jordan--Hölder Theorem. Properties of module lengths. Notes.
Mar.01. Classifying simple modules of path algebras of acyclic quivers. Notes.
Mar.03. Representations of quivers vs. modules of path algebras. Notes. Homework (tex).
Mar.05. Midterm review. Midterm I (available on Canvas from 5pm of Mar. 5 to 5pm of Mar. 6).
Mar.08. More on representations of quivers. Notes.
Mar.10. Bounded quiver algebras. Schur's Lemma. Notes. Homework (tex).
Mar.12. Applications of Schur's Lemma. Simple modules of quotients of k[x]. Notes.
Mar.15. Class cancelled due to winter storm.
Mar.17. Overview of semisimple modules, semisimple algebras, and Maschke's Theorem. Notes. Homework (tex).
Mar.19. Equivalent definitions of semisimple modules. Operations preserving sesisimplicity. Notes.
Mar.22. Semisimple algebras. Operations preserving semisimplicity of algebras. Notes.
Mar.24. Properties of Jacobson radicals, Part 1. Notes. Homework (tex).
Mar.26. Properties of Jacobson radicals, Part 2. Notes.
Mar.29. Examples and applications of Jacobson radicals. Notes.
Mar.31. Spring Pause (not very well defined, don't ask) Lecture I: homework discussion.
Apr.02. Spring Pause Lecture II: some applications of algebra representations.
Apr.05. The Artin-Wedderburn Theorem: statement, proof ingredients, and proof strategy. Notes.
Apr.07. The Artin-Wedderburn Theorem: endomorphism algebras, matrices of morphisms. Notes. Homework (tex).
Apr.09. The Artin-Wedderburn Theorem: finishing the proofs. Notes.
Apr.12. The Artin-Weddeburn Theorem: summary, corollaries and first examples. Notes.
Apr.14. Maschke's theorem. Notes. Homework (tex).
Apr.16. Combining Artin-Wedderburn and Maschke. Notes.
Apr.19. More on Artin-Wedderburn decompositions for finite groups. Notes.
Apr.21. Homework discussion. Final Exam announced (available on Canvas from 11:59 am of May 1 to 11:59 pm of May 2). Notes. Homework (tex).
Apr.23. Group characters. Notes.
Apr.26. Properties of characters and character tables. Notes.
Apr.28. Statement of the Krull-Schmidt theorem. Course review. Notes.