Expressing Elements as Products of Irreducibles in Unique Factorization Domains

In summary, the conversation discusses how to show that an element in an integral domain can be factored into irreducibles using the assumption that every prime ideal contains a principal ideal. The speaker suggests considering the principal ideal of b and finding a maximal proper principal ideal containing it, then continuing this procedure until the element is expressed as a product of irreducibles. However, the conversation ends with the realization that the fact that every prime ideal contains a principal ideal can be used to construct a sequence of principal ideals whose intersection is the principal ideal generated by b, enabling the expression of b as a product of irreducibles.
  • #1
EbolaPox
101
1
I'm having a bit of trouble with some ring theory I've been reading about, specifically unique factorization domains. I'm not really clear on how one would go about showing that an element can be factored into irreducibles

Homework Statement


Let [tex]R [/tex] be an integral domain such that every prime ideal in R$ contains a principal prime ideal [tex] (a) [/tex] , where [tex] a \neq 0 [/tex].

The Attempt at a Solution



Let [tex] b \in R [/tex]. I need to show that I can express b as a product of irreducibles. I'm not too sure how my assumption can help me out here. I do know that if [tex] c[/tex] is irreducible, then [tex] (c) [/tex] is maximal in the set of proper principal ideals. So, maybe if I consider the principal ideal of b, I can find a [tex] c_1 [/tex] such that [tex] (b) \subset (c_1) [/tex] and so [tex] c_1 [/tex] divides b. Therefore, I have [tex] b = c_1 x [/tex] where [tex] c_1 [/tex] is irreducible. I then thought I could apply the same idea to [tex] x[/tex] and get [tex] (x) \subset (c_2) [/tex], where [tex] c_2 [/tex] is irreducible and hence [tex] x = x_2 c_2 , b = c_1 c_2 x_2[/tex]. But, I'm not sure if this makes sense. I'm not sure if I can necessarily even find a maximal proper principal ideal containing b. I then thought I could "continue" this procedure, but I'm not sure how to know when this will end and I'm not using my assumptions at all. I need to somehow use the fact that a prime ideal contains a principal ideal. I have no idea how to use this idea.

I'm not looking for a full solution, I'd just like a helpful hint in the right direction. Thanks!EDIT: Never mind, I figured it out.
 
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  • #2
You can use the fact that every prime ideal contains a principal ideal to construct a sequence of principal ideals whose intersection is the principal ideal generated by b. Then you can use the fact that a principal ideal is a product of irreducibles to factor b into irreducibles.
 

Related to Expressing Elements as Products of Irreducibles in Unique Factorization Domains

What is a Unique Factorization Domain (UFD)?

A Unique Factorization Domain is a type of mathematical structure in which every nonzero, nonunit element can be uniquely expressed as a product of irreducible elements (also known as prime elements).

How is a UFD different from other types of rings?

Unlike other types of rings, such as integral domains or principal ideal domains, UFDs have the property that every nonzero, nonunit element can be factored into a unique product of irreducible elements. This means that there is only one way to write a given element as a product of primes.

What are some examples of UFDs?

The most common examples of UFDs are the ring of integers (Z) and the polynomial ring over a field (F[x]). Other examples include the ring of Gaussian integers (Z[i]) and the ring of polynomials in several variables (F[x,y]).

How can one determine if a ring is a UFD?

One way to determine if a ring is a UFD is to check if it satisfies the two main properties: every nonzero, nonunit element can be factored into a unique product of irreducible elements, and any two irreducible factorizations of an element are equivalent (meaning they differ only by a unit factor).

What are the applications of UFDs in science?

UFDs are important in many areas of mathematics and science, including number theory, algebraic geometry, and coding theory. They also have applications in physics, such as in the study of symmetry groups and the classification of particles in quantum mechanics.

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