Etingof–Rains conjecture on Hilbert series of irreducible Cherednik-algebra quotients

Let n=kp+rn=kp+r with 0r<p0\le r<p. Define

[k]z=1zk1z,[k]z!=[k]z[k1]z[1]z,[k]_z=\frac{1-z^k}{1-z},\qquad [k]_z!=[k]_z[k-1]_z\dotsm [1]_z,

and

Qr(n,z)=(n1r1)zr+1+i=0r(nr2+ii)zi.Q_r(n,z)=\binom{n-1}{r-1}z^{r+1}+\sum_{i=0}^{r}\binom{n-r-2+i}{i}z^i.

Here Lt,c\mathcal{L}_{t,c} is the irreducible quotient of the polynomial representation of the rational Cherednik algebra, and cc is generic. Etingof–Rains conjecture. The Hilbert series of Lt,c\mathcal{L}_{t,c} has the form

hL0,c(z)=[r]z![p]zQr(n,z)h_{\mathcal{L}_{0,c}}(z)=[r]_z![p]_zQ_r(n,z)

and

hL1,c(z)=[p]zn1[r]zp![p]zp!Qr(n,zp).h_{\mathcal{L}_{1,c}}(z)=[p]_z^{n-1}[r]_{z^p}![p]_{z^p}!Q_r\left(n,z^p\right).

This conjecture gives the proposed Hilbert-series formula in the general case n=kp+rn=kp+r and is reported as unpublished. The formula holds in the cases established in the source and in the earlier work of Devadas and Sun, while the general case remains open.

Sources & referencesView supporting material

Primary source

Merrick Cai and Daniil Kalinov, “The Hilbert Series of the Irreducible Quotient of the Polynomial Representation of the Rational Cherednik Algebra of Type A_n-1 in Characteristic p for p|n-1”, arXiv:1811.04910 (2021).

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