2. Groups Flashcards
Group
a group is a set equipped with a binary operation that combines any two elements to form a third element in such a way that conditions called group axioms are satisfied
4 group axioms
- Closure: for all x,y in G we have xy in G
- Associativity: (xy)z=x(yz)
- Identity Element: there exists an e such that ex=xe=x
- Inverses: xy=yx=e
Abelian Group
A group whose binary operation is commutative.
Order of a Group
The number |G| elements in the set G
Uniqueness
The indentity element and inverse of x belonging to G is unique
Symmetric Group
The set of all permutations of the set X under composition
Cyclic Group
there exists an element x in G such that for every y in G there is an m such that y=x^m
Example of Cyclic group
The set of invertible elements where m would be -1
Generator of Cyclic Group
The letter x such that y=x^m
Generator Set
A smaller set of objects, together with a set of operations that can be applied to it that result in a larger collection of objects
Dihedral Group
The finite group of symmetries of a regular polygon. It is non abelian and example of connection between groups and geometry.