2026/27 Undergraduate Module Catalogue

MATH3125 Groups and Symmetry

20 Credits Class Size: 300

Module manager: Kevin Houston
Email: K.Houston@leeds.ac.uk

Taught: Semester 1 (Sep to Jan) View Timetable

Year running 2026/27

Pre-requisite qualifications

None

Pre-requisites

MATH1120 Introduction to Group Theory

Mutually Exclusive

MATH3071 Groups and Symmetry

Module replaces

MATH3071 Groups and Symmetry

This module is not approved as a discovery module

Module summary

Group theory is the mathematical study of symmetry. Groups arisenaturally in both pure and applied mathematics, for example in the studyof permutations of sets, rotations and reflections of geometric objects,symmetries of physical systems and the description of molecules, crystalsand materials. They also have beautiful applications in countingproblems, where we count objects up to symmetry. For example, grouptheory can answer questions like: "How many distinct ways can the facesof a cube be coloured with m different colours, up to rotation of thecube?"

Objectives

On completion of this module, students should be able to ...

To review and develop the basic notions and theorems of group theory.
To introduce the notion of homomorphism.
To introduce the notion of quotient group.
To recall the notion of a group acting on a set and to develop its properties and applications.
To study the powerful Sylow theorems which give information on the structure of an arbitrary finite group in terms of the prime divisors of its order; to use group actions in this study.
To introduce Pólya counting theory and how it is used to count objects up to symmetry.
To develop the skills of rigorous logical argument and problem-solving in the context of group theory and symmetry.

Learning outcomes

On successful completion of the module students will be able to:
1. Prove and use basic results on groups, subgroups, and homomorphisms.
2. Represent a group by permutations;
3. Calculate quotient groups and prove theorems about them;
4. Prove and use basic results of group actions;
5. State and use the Orbit-Stabiliser Theorem;
6. Apply Pólya counting theory and Burnside’s Lemma to somesimple counting problems;7. Use Sylow's theorems to show that a group is not simple.

Skills outcomes

On successful completion of the module students will be able to:
a) Creatively solve unseen problems
b) Communicate technical mathematics in written form
c) Identify areas required for improvement
d) Develop critical thinking
e) Manage workload

Syllabus

Revision of basic properties of groups.
Subgroups, Lagrange's Theorem.
Symmetric group, sign of a permutation, cycle decomposition
.Homomorphisms.
Quotient groups and isomorphism theorems.
Group actions.
Orbit-Stabiliser Theorem, application to symmetric group, Cayley'sTheorem.
Conjugacy, centralisers.
Burnside's Lemma, Pólya counting theory.
Sylow theorems and applications, simple groups.

Teaching Methods

Delivery type Number Length hours Student hours
Lectures 44 1 44
Private study hours 156
Total Contact hours 44
Total hours (100hr per 10 credits) 200

Opportunities for Formative Feedback

Regular pieces of coursework which students may submit for formative feedback

Reading List

Check the module area in Minerva for your reading list

Last updated: 30/04/2026

Errors, omissions, failed links etc should be notified to the Catalogue Team