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### Computing the non-normal locus

Input
, .
We assume that is a radical ideal.
Output
Generators for such that .

1. Compute an ideal as described in Sect. .
2. Compute a non-zerodivisor : choose an -linear combination of the generators of and test if is zero, by using that is a non-zerodivisor iff .

A sufficiently general linear combination gives a non-zerodivisor.

3. Compute a test ideal , e.g., or .
4. Compute generators for as -module.
5. Return .

Christoph Lossen
2001-03-21