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Dec 22, 2016 at 20:26 answer added Abdelmalek Abdesselam timeline score: 2
Dec 21, 2016 at 14:01 answer added Robert Bryant timeline score: 7
Dec 21, 2016 at 9:24 vote accept evgeny
Dec 21, 2016 at 8:43 answer added Friedrich Knop timeline score: 10
Dec 21, 2016 at 7:47 comment added evgeny @YCor, edited: I hope that now $\mathbb C[W]^{\mathbb C^* \rtimes \mathbb Z/2\mathbb Z}$ is right?
Dec 21, 2016 at 7:45 history edited evgeny CC BY-SA 3.0
corrected about degree 4, not 2
Dec 21, 2016 at 7:29 comment added YCor @evgeny, you should edit further, since all expectations about $C[sq]$ make little sense now.
Dec 21, 2016 at 6:21 history edited evgeny CC BY-SA 3.0
corrected, thanks!
Dec 20, 2016 at 21:49 comment added Robert Bryant @evgeny I hate to have to point this out, but if $\omega$ is a $3$-form then $\omega^2 \equiv 0$ (after all, $\omega\wedge\eta = -\eta\wedge\omega$ when $\omega,\eta\in\Lambda^3$), so your attempt to construct an invariant this way fails. In fact, there is a nonzero invariant polynomial under $\mathrm{SL}(6,\mathbb{C})$ and it does generate the ring of invariants, but it is irreducible of degree $4$, not degree $2$.
Dec 20, 2016 at 21:11 comment added Sasha Vinberg-Popov, Invariant theory (VINITI, Algebraic geometry - IV), and references therein.
Dec 20, 2016 at 20:57 comment added evgeny @Sasha, could you give me a reference or a name for this result?
Dec 20, 2016 at 20:45 comment added Sasha It does. This is a well-known result in invariant theory.
Dec 20, 2016 at 20:41 history asked evgeny CC BY-SA 3.0