Take the 2-minute tour ×
MathOverflow is a question and answer site for professional mathematicians. It's 100% free, no registration required.

In the paper 'FINITE LINEAR GROUPS WHOSE RING OF INVARIANTS IS A COMPLETE INTERSECTION' by VICTOR KAC AND KEI-ICHI WATANABE published in BULLETIN (New Series) OF THE AMERICAN MATHEMATICAL SOCIETY Volume 6, Number 2, March 1982, it is said in remark 2 of page no 222 that for any finite subgroup $G$ of $GL_2(\mathbb{C})$ the ring of invariance $\mathbb{C}[X_1, X_2]^G$ is always a complete itersection ring without any reference. Can anyone kindly tell me a reference for this result? Thanking you.

share|improve this question
    
1  
I am also considering finite subgroups of $GL_2\mathbb(C)$ which are not contained in $SL_2\mathbb(C)$ –  Anjan Gupta Mar 11 '11 at 20:06
3  
Here's a link to the paper: ams.org/journals/bull/1982-06-02/S0273-0979-1982-14989-8 . The remark is wrong, almost certainly a typo. –  Graham Leuschke Mar 11 '11 at 20:24
9  
For an explicit example, take $G$ to be the three-element group generated by $\mathrm{diag}(e^{2\pi i/3},e^{2\pi i/3})$. The invariant ring is $\mathbb{C}[x^3,x^2y,xy^2,y^3]$, which is not even Gorenstein. –  Graham Leuschke Mar 11 '11 at 20:32
1  
As far as I know, the article of Kac and Watanabe is the state of the art. Just ignore this typo. Or see this section of Neusel's book, and the references there: books.google.com/… –  Graham Leuschke Mar 12 '11 at 1:14

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.