The comparison conjecture for canonical and bidual canonical degrees

Let (R,m)({\mathbf R},{\mathfrak m}) be a Cohen--Macaulay local ring of dimension 11 with canonical ideal C\mathcal{C}. Let (c)(c) be a minimal reduction of C\mathcal{C}, so that C=(c):((c):C)\mathcal{C}^{**}=(c):((c):\mathcal{C}).

Comparison conjecture. The inequality

cdeg(R)bideg(R)\operatorname{cdeg}({\mathbf R})\geq \operatorname{bideg}({\mathbf R})

holds. Equivalently,

λ(C/(c))λ(C/C),\lambda(\mathcal{C}/(c))\geq\lambda(\mathcal{C}^{**}/\mathcal{C}),

or

e0(C)+λ(R/C)2λ(R/C).\operatorname{e}_0(\mathcal{C})+\lambda({\mathbf R}/\mathcal{C}^{**})\geq 2\lambda({\mathbf R}/\mathcal{C}).

Here cdeg(R)\operatorname{cdeg}({\mathbf R}) and bideg(R)\operatorname{bideg}({\mathbf R}) denote the canonical degree and bidual canonical degree, respectively. The conjecture asks whether the canonical degree always dominates the bidual canonical degree in dimension one; the supplied text gives no resolution.

Sources & referencesView supporting material

Primary source

J. P. Brennan, L. Ghezzi, J. Hong, L. Hutson and W. V. Vasconcelos, “Canonical Degrees of Cohen-Macaulay Rings and Modules: a Survey”, arXiv:2006.14401 (2020).

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