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Constructing (Almost) Rigid Rings and a UFD Having Infinitely Generated Derksen and Makar-Limanov Invariants |
Canad. Math. Bull. 53(2010), 77-86
Published:2009-12-04
Printed: Mar 2010
Printed: Mar 2010
- David Finston
- Stefan Maubach
Abstract
An example is given of a UFD which has an infinitely generated Derksen invariant. The ring is "almost rigid" meaning that the Derksen invariant is equal to the Makar-Limanov invariant. Techniques to show that a ring is (almost) rigid are discussed, among which is a generalization of Mason's abc-theorem.
| MSC Classifications: |
14R20 - Group actions on affine varieties [See also 13A50, 14L30] 13A50 - Actions of groups on commutative rings; invariant theory [See also 14L24] 13N15 - Derivations |