1) <R, +> is an abelian group.

2) Multiplication is closed and associative.

3) For all a, b, c contained in R, the left distributive law, a(b + c) = (ab) + (ac), and the right distributive law, (a + b) = (ac) + (bc), hold.

** Definition:** A ring in which the multiplication is commutative is a

** Definition:** If

** Definition:** An

If an integral domain is such that every nonzero element has a multiplicative inverse, then it is a field. Although many integral domains, such as the integers **Z**, do not form a field, every integral domain can be regarded as being *contained* in a certain field, ** a field of quotients of the integral domain**. For example, the integers are contained in the field

An ideal is to a ring as a normal subgroup is to a group.

** Definition:** Let

*[the index

where **a _{i}** is in

If **F** is a field, then **F[x]** -- the set of all polynomials in an indeterminate **x** with coefficients in **F** -- is an integral domain. Note that **F[x]** is not a field, for **x** is not a unit in **F[x]**. An element of a field is a **unit** of that field if it has a multiplicative inverse; and there is no polynomial **f(x) in F[x]** such that **x•f(x) = 1**. For that to be the case, we would have to have the possibility of negative exponents for the **x's**, which we don't by the definition above.

** Definition:** Let

If **f(α) = 0**, then **α** is a **zero of f(x).**

[A **homomorphism** can be thought of as a map that preserves structure and computational integrity.]

If ** f(x)** has no zero in

** Theorem:** (Fundamental Homomorphism Theorem). Let

[An **isomorphism** is a homomorphism that is one-to-one and onto. Intuitively, the domain and its image under an isomorphism contain the same number of elements [cardinality] in their sets and respect the same operations of addition and multiplication. **Canonical** just means **natural** in the sense of **what one would expect**.]

This theorem suggests that we try to form **E** by forming a factor ring **F[x]/N** for some suitable ideal **N** of **F[x]**.

__Theorem:__**F[x]/(p(x))** is a field if and only if **p(x)** is irreducible.

** The Complex Number Field:** Let

= (x

Thus **α** is a zero of (**x ^{2} + 1**) in

We're identifying **<x ^{2} + 1>** with zero through the factor ring where the kernel is the zero element, analogous to a factor group, the role of normal subgroup being played by the ideal. The polynomial

We're basically extending the field **R** to **C**; that is, in the act of **deflating**, we **expand**. The *external appearance* of **R[x]** shrinks and at the same instant its internal configuration embeds itself in the newly defined algebraic structure, *infusing* its integral domain structure into that of the field -- **R[x]/<x ^{2} + 1>**.

This is very similar to how the field of rational numbers, **Q**, includes the integral domain of integers, **Z**. **Z** *before* the transition is all of the universe, *after*, it resides *inside* the more complex **Q**. Imagine the integers spread out on a line, suddenly the formerly blank space between pairs is filled with an infinite number of fractions -- *quotients of integers*. By virtue of these fractions, the non-zero integers take on the new role of units. **Z** shrinks in relative size, yet grows, through sub-divisions, to a vast sea of multi-dimensional relationships and interconnections.

Here's what's happening: The axiom we needed to jump from an integral domain to a field was the existence of a multiplicative inverse for each non-zero polynomial -- **f(x) + <p(x)>** -- in our quotient ring. Those are our **units**. A proof that they exist can be found at the link on **Quotient Rings** below. That gives us the added internal structure of an **abelian multiplicative group** and hence, a field. The symmetry of *connections* after collapse increases by a whole new order. Topologically, a *refinement* has been made.

If you're interested in understanding how **Quotient Rings** work, what constitutes a **coset**, etcetera, check out Quotient Rings of Polynomial Rings in HTML format by Professor Bruce Ikenaga of Millersville University.

Here's the beauty and magic of this. Regardless of whether or not you understand the theory, the math, what is going on is quite remarkable. We're creating an extension of an integral domain to a field for purposes of solving an irreducible polynomial, one that's unsolvable in the environment restricted to the real numbers. In the world of algebraic hierarchy, a field is one level above an integral domain in structural identity and therefore in complexity, similar to the difference in atom arrangements between liquid water and ice crystals. So, we're generating a more complex structure by superimposing a conditional symmetry on the parent structure through the process of factoring. A transformation to a new species occurs, one whose interconnections are far more intricate.

By identifying the irreducble polynomial with the zero element of the factor ring, we map *all* polynomials of the parent ring that contain the irreducble as a factor to the kernel [the maximal ideal], the zero element of the factor ring, our manufactured field. All other non-zero polynomials [units] are considered congruent if they differ by a multiple of the zero-class -- **[x ^{2} + 1]** -- and are thereby grouped into cosets of equivalence classes.

By placing boundaries, setting initial conditions, on something infinite and incomprehensible, we make it comprehensible. To reiterate, by partitioning the ring of polynomials with real number coefficients -- **R[x]** -- into distinct, disjoint cosets modulo **<x ^{2} + 1>** we are essentially

To paraphrase from above: Then **R( i) = R[x]/<x^{2} + 1>** and consists of all elements of the form

By factoring the parent ring with the stamp of the irreducible polynomial, we *force* **(x ^{2} + 1)** to equal zero and thereby introduce the number

The mathematics of evolution.

For **p(x) = (x ^{2} + 1):**

The real line is the function line, each point, a function or polynomial, **f(x)**. To it is added a function-multiple of **i = p(x)**. The linear combination, **f(x) + <p(x)>**, maps isomorphically to **a + bi** on the complex plane.

The field of polynomials, **R[x]/<p(x)>** equal to **R(i) ≈ C** can be mapped to the complex plane by cosines and sines.

The exponential function **e ^{iθ}** equals the sum of the power series expansions for

We get:
**e ^{i f(x)} = cos(f(x)) + i sin(f(x))**

Replacing **θ** with **f(x) in R[x]** maps them isomorphically to the complex plane. Each non-zero number on the Real line must equal, or is isomorphic to, a function in **R[x]**.

The zero equivalence class, **[p(x)]**, is orthogonal to the function line, and is therefore at 90 degrees, or **π/2** radians. Therefore, for **x = 0**, the cosine of **f(x) + 0[p(x)]** equals one, and the sine equals zero. And for a nonzero multiple of **[p(x)]**, the sine **[p(x)]**, or the **i axis** in the complex plane, is equal to one (1) and the cosine, zero.

Review by Brian E. Blank | PDF File