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    Answer by user "VA" to question :

    "This is just to add 1% to Dmitri's 99% complete answer. Change the coordinates to $w_0,\dots, w_{n-1}$ defined by the formula

    $$ w_i = x_0 + \mu^i x_1 + \mu^{2i} x_2 + \dots, $$

    where $\mu$ is a primitive $n$-th root of identity. Then the ring of invariants is the subring of monomials

    $$ w_0^{k_0}\dots w_{n-1}^{k_{n-1}} \quad \text{such that}\quad n\ |\ k_1 + 2k_2 + \dots (n-1) k_n$$

    and a set of generators can be obtained by taking minimal such monomials (i.e. not divisible by smaller such monomials). And relations between these generators are of the form (monomial in $w_i$) = (another monomial in $w_i$). That's a pretty easy presentation by any standard.

    P.S. This works over $\mathbb C$ or any ring containing $1/n$ and $\mu$."

    Notice that this answer, while not adding any new ideas, noticeably improves upon the exposition of Dmitri's one. It is voted +3, so I am surprised the author was able to delete it in the first place...

    • CommentAuthorquid
    • CommentTimeMar 24th 2013

    Only regarding the final comment: Since there is a badge [disciplined] for deleting a post with at least +3 the fact that it was possible to delete it does not seem so suprising to me. (AFAIK only accepted answers, and questions with good [in the sense of score] answers are problematic to delete.)


    You cannot delete your own posts in the following cases:

    1. You are an unregistered user.
    2. You are trying to delete an accepted answer.
    3. You are trying to delete a question with an upvoted answer.

    This is my experience from SE 2.0, but I believe that this feature is shared with MO and its obsolete software.


    There is an old story here and I think this answer was deleted as part of it. You might be able to figure things out if you check meta threads around the end of April 2010. I don't think anybody would mind if it got undeleted.


    Ah, I see! Voting to undelete then, and if possible to scan through the other deleted posts from the same author.

    @FGD: I would mind greatly if the answer were undeleted, purely on the grounds that I would want to respect the wishes of the author.
    • CommentAuthorabatkai
    • CommentTimeMar 25th 2013
    @justcurious: is you post here something, it is not yours anymore. If the community feels that your contribution is important and useful, then you have to accept that it becomes visible to everyone. At the moment it is visible to quite a few users anyway.