Commutative Algebra

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Field of Fractions

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Commutative Algebra

Definition

A field of fractions is a construction that takes an integral domain and creates a field where every element can be expressed as a fraction with a numerator and a denominator from the original integral domain, except for zero. This construction allows us to perform division by non-zero elements, facilitating the exploration of properties that are not always available in the original domain. The concept is key in understanding how integral domains relate to fields, especially when discussing prime and maximal ideals, localization, and properties of integrally closed domains.

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5 Must Know Facts For Your Next Test

  1. The field of fractions of an integral domain is unique up to isomorphism, meaning any two constructions will yield isomorphic fields.
  2. If you have an integral domain $D$, its field of fractions is denoted as $K(D)$, where every element can be written as $a/b$ with $a,b \in D$ and $b \neq 0$.
  3. Fields of fractions are crucial for understanding how integral domains can behave similarly to fields, particularly when dealing with linear equations.
  4. A field of fractions allows us to apply techniques from field theory to study properties of the original integral domain.
  5. In the context of prime and maximal ideals, fields of fractions help determine whether certain elements can be factored or if certain polynomials have roots.

Review Questions

  • How does the field of fractions relate to the structure and properties of an integral domain?
    • The field of fractions provides a way to extend an integral domain into a field where division by non-zero elements is possible. This extension reveals more about the original domain's properties, such as whether certain equations can be solved. By analyzing the relationships between elements in the field of fractions and their counterparts in the integral domain, we gain insights into concepts like factorization and divisibility.
  • Discuss how fields of fractions interact with prime and maximal ideals within an integral domain.
    • When we take the field of fractions from an integral domain, prime ideals correspond to certain behaviors in this larger structure. Specifically, if an ideal is prime in the integral domain, its image in the field of fractions has special properties regarding irreducibility. Maximal ideals also reflect significant relationships in this context, particularly as they lead to fields that represent residue classes, shedding light on which elements can create new fields through division.
  • Evaluate the importance of constructing a field of fractions when working with localization and integrally closed domains.
    • Constructing a field of fractions is essential when localizing an integral domain because it allows for more versatile manipulation of elements, specifically enabling division by any non-zero element. This flexibility is critical in determining how certain integrally closed domains function since it helps establish whether they maintain closure under various operations. By using the field of fractions alongside localization, one can investigate deeper properties of rings, such as their dimension and singularities.
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