Maps from Feigin and Odesskii's elliptic algebras to twisted homogeneous coordinate rings
Abstract: The elliptic algebras in the title are connected graded $\mathbb{C}$-algebras, denoted $Q_{n,k}(E,\tau)$, depending on a pair of relatively prime integers $n>k\ge 1$, an elliptic curve $E$, and a point $\tau\in E$. This paper examines a canonical homomorphism from $Q_{n,k}(E,\tau)$ to the twisted homogeneous coordinate ring $B(X_{n/k},\sigma',\mathcal{L}'{n/k})$ on the characteristic variety $X{n/k}$ for $Q_{n,k}(E,\tau)$. When $X_{n/k}$ is isomorphic to $Eg$ or the symmetric power $SgE$ we show the homomorphism $Q_{n,k}(E,\tau) \to B(X_{n/k},\sigma',\mathcal{L}'{n/k})$ is surjective, that the relations for $B(X{n/k},\sigma',\mathcal{L}'{n/k})$ are generated in degrees $\le 3$, and the non-commutative scheme $\mathrm{Proj}{nc}(Q_{n,k}(E,\tau))$ has a closed subvariety that is isomorphic to $Eg$ or $SgE$, respectively. When $X_{n/k}=Eg$ and $\tau=0$, the results about $B(X_{n/k},\sigma',\mathcal{L}'{n/k})$ show that the morphism $\Phi{|\mathcal{L}_{n/k}|}:Eg \to \mathbb{P}{n-1}$ embeds $Eg$ as a projectively normal subvariety that is a scheme-theoretic intersection of quadric and cubic hypersurfaces.
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