Associated Primes

Definition

Associated primes are prime ideals that are linked to the structure of a module over a ring, specifically those prime ideals that correspond to the annihilator of elements in the module. They play a crucial role in understanding the decomposition of modules and the depth of rings, connecting to the dimension theory and Cohen-Macaulay properties, which explore how these ideals reveal information about the singularities and geometric properties of the underlying space.

5 Must Know Facts For Your Next Test

1. Each associated prime corresponds to an element of the module whose annihilator is that prime ideal.
2. In Noetherian rings, associated primes can be used to characterize modules, helping to determine whether they are Cohen-Macaulay based on their depth and dimension.
3. The set of associated primes can provide valuable information about singularities in algebraic geometry, as they often relate to points where certain functions fail to behave well.
4. An important result is that for any finitely generated module over a Noetherian ring, the set of associated primes is finite.
5. Associated primes are central to Hilbert's Nullstellensatz, connecting algebraic geometry with commutative algebra by linking ideals and varieties.

Review Questions

• How do associated primes relate to the depth and dimension of a module over a Noetherian ring?
  • Associated primes directly connect to both depth and dimension by indicating where the module may have 'depth' deficits. Specifically, if a module has associated primes, it may indicate that there are elements that do not contribute fully to its depth. In Noetherian rings, understanding these relationships helps determine whether a module is Cohen-Macaulay, which requires that its depth equals its dimension.
• What role do associated primes play in characterizing Cohen-Macaulay rings, and why are they important for understanding singularities?
  • In Cohen-Macaulay rings, associated primes help identify whether the ring has consistent depth throughout its structure. This consistency indicates that all localizations at prime ideals behave similarly, revealing insights into singularities in algebraic varieties. By analyzing associated primes, one can understand the nature and number of singular points in geometrical representations derived from these algebraic structures.
• Evaluate how associated primes contribute to the study of modules over Noetherian rings and their implications for algebraic geometry.
  • Associated primes serve as a vital tool in studying modules over Noetherian rings because they highlight where modules may fail to meet certain conditions like being Cohen-Macaulay. This understanding extends into algebraic geometry by linking the behavior of these modules with geometric properties, such as singular points in varieties. By examining associated primes, one gains insights into both algebraic structures and their corresponding geometric manifestations, revealing deeper relationships between algebra and geometry.

Related terms

Prime Ideal: A prime ideal is an ideal in a ring such that if the product of two elements is in the ideal, then at least one of those elements must be in the ideal.

Support: The support of a module is the set of prime ideals for which the localization of the module at that prime ideal is not zero, essentially indicating where the module has 'activity'.

Depth: The depth of a ring or module is a measure of how many elements can be found that do not belong to any associated prime, providing insights into its structural complexity.