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MA251 Algebra 1: Advanced Linear Algebra

Lecturer: Daan Krammer

Term(s): Term 1

Status for Mathematics students:

Core for Maths.

This module will be examined in Week 30, the first week of Term 3.

Commitment: 30 one-hour lectures plus six assignments

Assessment: Assignments (15%), two-hour examination (85%).

Prerequisites: MA106 Linear Algebra and MA132 Foundations (MA138 Sets and Numbers for non-maths students)

Leads To: third year algebra modules, such as MA3D5 Galois Theory, MA377 Rings and modules. Some of the theory is also needed in MA371 Qualitative Theory of ODEs

Content: This module is a continuation of First Year Linear Algebra. In that course we studied conditions under which a matrix is similar to a diagonal matrix, but we did not develop methods for testing whether two general matrices are similar. Our first aim is to fill this gap for matrices over  {\mathbb C} . Not all matrices are similar to a diagonal matrix, but they are all similar to one in Jordan canonical form; that is, to a matrix which is almost diagonal, but may have some entries equal to 1 on the superdiagonal.

We next study quadratic forms. A quadratic form is a homogeneous quadratic expression  \sum a_{ii}x_ix_j in several variables. Quadratic forms occur in geometry as the equation of a quadratic cone, or as the leading term of the equation of a plane conic or a quadric hypersurface. By a change of coordinates, we can always write  q(x) in the diagonal form  \sum a_ix_i^2. . For a quadratic form over  \R , the number of positive or negative diagonal coefficients  a_i is an invariant of the quadratic form which is very important in applications.

Finally, we study matrices over the integers  {\mathbb Z} , and investigate what happens when we restrict methods of linear algebra, such as elementary row and column operations, to operations over  {\mathbb Z} . This leads, perhaps unexpectedly, to a complete classification of finitely generated abelian groups.

Aims: To develop further and to continue the study of linear algebra, which was begun in Year 1.

To point out and briefly discuss applications of the techniques developed to other branches of mathematics, physics, etc.

Objectives: By the end of the module students should be familiar with: the theory and computation of the the Jordan canonical form of matrices and linear maps; bilinear forms, quadratic forms, and choosing canonical bases for these; the theory and computation of the Smith normal form for matrices over the integers, and its application to finitely generated abelian groups.

Books:

P M Cohn, Algebra, Vol. 1, Wiley

I N Herstein, Topics in Algebra, Wiley.

Neither is essential, but are a good idea if you are intending to study further algebra modules.

Recommended Syllabus
 

Additional Resources

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Year 1 regs and modules
G100 G103 GL11 G1NC

yr2.jpg
Year 2 regs and modules
G100 G103 GL11 G1NC

yr3.jpg
Year 3 regs and modules
G100 G103

yr4.jpg
Year 4 regs and modules
G103

Archived Material
Past Exams
Core module averages