# Finite field

Main Article
Talk
Related Articles  [?]
Bibliography  [?]
Citable Version  [?]

This editable Main Article is under development and not meant to be cited; by editing it you can help to improve it towards a future approved, citable version. These unapproved articles are subject to a disclaimer.

A finite field is a field with a finite number of elements; e,g, the fields  (with the addition and multiplication induced from the same operations on the integers). For any primes number p, and natural number n, there exists a unique finite field with pn elements; this field is denoted by  or  (where GF stands for "Galois field").

## Proofs of basic properties:

### Finite characteristic:

Let F be a finite field, then by the piegonhole principle there are two different natural numbers number n,m such that . hence there is some minimal natural number N such that . Since F is a field, it has no 0 divisors, and hence N is prime.

### Existence and uniqueness of Fp

To begin with it is follows by inspection that  is a field. Furthermore, given any other field F' with p elements, one immediately get an isomorphism  by mapping .

### Existence - general case

working over , let . Let F be the splitting field of f over . Note that f' = -1, and hence the gcd of f,f' is 1, and all the roots of f in F are distinct. Furthermore, note that the set of roots of f is closed under addition and multiplication; hence F is simply the set of roots of f.

### Uniqueness - general case

Let F be a finite field of characteristic p, then it contains ; i.e. it contains a copy of . Hence, F is a vector field of finite dimension over . Moreover since the non 0 elements of F form a group, they are all roots of the polynomial ; hence the elements of F are all roots of f.

## The Frobenius map

Let F be a field of characteritic p, then the map  is the generator of the Galois group .