The hyperplane-section inequality for bi-canonical degree

Let (R,m)({\mathbf R},{\mathfrak m}) be a Cohen–Macaulay local ring with canonical ideal C\mathcal{C}. Let xx be regular modulo C\mathcal{C}, and suppose that C\mathcal{C} is equimultiple. Set S=R/(x){\mathbf S}={\mathbf R}/(x). The image of C\mathcal{C} in S{\mathbf S} is a canonical ideal, denoted by D=(C,x)/(x)\mathcal{D}=(\mathcal{C},x)/(x).

Hyperplane-section conjecture.

bideg(R)bideg(R/(x)).\operatorname{bideg}({\mathbf R})\geq \operatorname{bideg}({\mathbf R}/(x)).

Equivalently, with D\mathcal{D} as above, the proposed inequality compares bideg(R)=deg(R/C)deg(R/C)\operatorname{bideg}({\mathbf R})=\deg({\mathbf R}/\mathcal{C})-\deg({\mathbf R}/\mathcal{C}^{**}) with bideg(S)=deg(S/D)deg(S/D)\operatorname{bideg}({\mathbf S})=\deg({\mathbf S}/\mathcal{D})-\deg({\mathbf S}/\mathcal{D}^{**}). The source presents this as a desirable comparison modeled on the corresponding canonical-degree inequality; no resolution is given.

Sources & referencesView supporting material

Primary source

L. Ghezzi, S. Goto, J. Hong, H. L. Hutson and W. V. Vasconcelos, “The Bi-Canonical Degree of a Cohen-Macaulay Ring”, arXiv:1711.09480 (2019).

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