system of parameters

{{Short description|Mathematical concept in dimension theory of local rings}}

{{More citations needed|date=May 2022}}

In mathematics, a system of parameters for a local Noetherian ring of Krull dimension d with maximal ideal m is a set of elements x₁, ..., x_d that satisfies any of the following equivalent conditions:

1. m is a minimal prime over (x₁, ..., x_d).
2. The radical of (x₁, ..., x_d) is m.
3. Some power of m is contained in (x₁, ..., x_d).
4. (x₁, ..., x_d) is m-primary.

Every local Noetherian ring admits a system of parameters.{{cite web|url=http://www.math.lsa.umich.edu/~hochster/711F07/L09.05.pdf | title=Math 711: Lecture of September 5, 2007 | publisher=University of Michigan| date=September 5, 2007 | accessdate=May 31, 2022}}

It is not possible for fewer than d elements to generate an ideal whose radical is m because then the dimension of R would be less than d.

If M is a k-dimensional module over a local ring, then x₁, ..., x_k is a system of parameters for M if the length of {{nowrap|M / (x₁, ..., x_k) M}} is finite.