16: An Introduction to Rings and Fields

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field extension

Field extensions are simple. Let's say
That field \(L\) is a subfield of \(K\),
Then it goes without mention,
Field \(K\)'s an extension
Of \(L\) — like a shell, in a way.

zqms, The Omnificent English Dictionary in Limerick Form

In our early elementary school days we began the study of mathematics by learning addition and multiplication on the set of positive integers. We then extended this to operations on the set of all integers. Subtraction and division are defined in terms of addition and multiplication. Later we investigated the set of real numbers under the operations of addition and multiplication. Hence, it is quite natural to investigate those structures on which we can define these two fundamental operations, or operations similar to them. The structures similar to the set of integers are called rings, and those similar to the set of real numbers are called fields.

In coding theory, highly structured codes are needed for speed and accuracy. The theory of finite fields is essential in the development of many structured codes. We will discuss basic facts about finite fields and introduce the reader to polynomial algebra.