Unit · year 2
MU-204 · Group Theory
Threads structure25 lectures6 theorems
The mathematics of symmetry, from Lagrange's theorem to the Sylow theorems.
Lectures
| L01 | Symmetry and the Group Axioms — |
| L02 | Examples: Cyclic, Dihedral, and Symmetric Groups — |
| L03 | Subgroups and the Subgroup Test — |
| L04 | Cyclic Groups and Their Subgroups — |
| L05 | Cosets and Partitions |
| L06 | Lagrange's Theorem |
| L07 | Consequences: Element Orders and Groups of Prime Order |
| L08 | Normal Subgroups — |
| L09 | Quotient Groups — |
| L10 | Homomorphisms and Kernels |
| L11 | The First Isomorphism Theorem |
| L12 | The Second and Third Isomorphism Theorems |
| L13 | Direct Products — |
| L14 | Group Actions |
| L15 | Orbits and Stabilisers |
| L16 | The Orbit–Stabiliser Theorem |
| L17 | Conjugacy Classes and the Class Equation |
| L18 | Cauchy's Theorem |
| L19 | p-Groups and Their Centres |
| L20 | The Sylow Theorems |
| L21 | Applying Sylow: Classifying Small Groups |
| L22 | The Structure of Finite Abelian Groups |
| L23 | The Symmetric and Alternating Groups — |
| L24 | Simplicity of Aₙ and Composition Series — |
| L25 | Synthesis: Structure Forced by Counting |
Theorems in this unit
T-057
Lagrange's theorem
The order of a subgroup divides the order of the group.
T-058
The orbit–stabiliser theorem
Orbit size times stabiliser size equals the group order.
T-059
The first isomorphism theorem
The image of a homomorphism is the quotient by its kernel.
T-060
Cauchy's theorem
If a prime divides the group order, an element of that order exists.
T-061
The Sylow theorems
Existence, conjugacy, and counting of maximal p-subgroups.
T-062
Structure of finite abelian groups
Every finite abelian group is a product of cyclic groups.