Regular local ring: Difference between revisions

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==Definition==
==Definition==


Serre's Regularity Criterion states that a [[Noetherian Ring|Noetherian]] [[local ring]] <math>A</math> is regular if and only if its [[global dimension]] is finite, in which case it is equal to the [[Krull dimension]] of <math>A</math>.
Let <math>A</math> be a Noetherian local ring with maximal ideal <math>\mathfrac{m}</math> and residual field <math>k=A/\mathfrac{m}</math>.  The following conditions are equivalent:
 
# The Krull dimension of <math>A</math> is equal to the dimension of <math>\mathfrac{m}/\mathfrac{m}^2</math> as a <math>k</math>-vector space.


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Revision as of 09:30, 2 December 2007

There are deep connections between algebraic (in fact, scheme-theoretic) notions of smoothness and regularity.

Definition

Let be a Noetherian local ring with maximal ideal Failed to parse (unknown function "\mathfrac"): {\displaystyle \mathfrac{m}} and residual field Failed to parse (unknown function "\mathfrac"): {\displaystyle k=A/\mathfrac{m}} . The following conditions are equivalent:

  1. The Krull dimension of is equal to the dimension of Failed to parse (unknown function "\mathfrac"): {\displaystyle \mathfrac{m}/\mathfrac{m}^2} as a -vector space.