Buchsbaum–Eisenbud conjectural resolution for Schur powers of a determinantal cokernel

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Let RR be a graded ring, let FF and GG be graded free RR-modules of ranks tt and t+c−1t+c-1, respectively, and let φ∗:G∗⟶F∗\varphi^*:G^*\longrightarrow F^* be a graded morphism. Suppose that depth⁡It−1(φ)R=2(c+1)\operatorname{depth}_{I_{t-1}(\varphi)}R=2(c+1). For the cokernel coker⁡(φp−1,1∗)\operatorname{coker}(\varphi^*_{p-1,1}), and in particular for ⋀2M\bigwedge^2M, consider the graded free resolution beginning with the displayed complexes.

Buchsbaum–Eisenbud conjectural resolution. A resolution of coker⁡(φp−1,1∗)\operatorname{coker}(\varphi^*_{p-1,1}) should always start out as

⋯⟶L2p−1(G)∗⊕Ap(F)⊗⋀tG∗⟶⋀p−1G∗⊗F∗⟶⋀pF∗⟶coker⁡(φp−1,1∗)⟶0.\cdots\longrightarrow L_2^{p-1}(G)^*\oplus A^p(F)\otimes\bigwedge^tG^*\longrightarrow\bigwedge^{p-1}G^*\otimes F^*\longrightarrow\bigwedge^pF^*\longrightarrow\operatorname{coker}(\varphi^*_{p-1,1})\longrightarrow0.

In particular, a resolution of ⋀2M\bigwedge^2M should always start out as

⋯⟶L21(G)∗⊕A2(F)⊗⋀tG∗⟶G∗⊗F∗⟶⋀2F∗⟶⋀2M⟶0.\cdots\longrightarrow L_2^1(G)^*\oplus A^2(F)\otimes\bigwedge^tG^*\longrightarrow G^*\otimes F^*\longrightarrow\bigwedge^2F^*\longrightarrow\bigwedge^2M\longrightarrow0.

Here LpqF=ker⁡(δp+1q−1)L_p^qF=\ker(\delta_{p+1}^{q-1}), and Ap(F)=coker⁡(⋀t−pF⟶⋀t−p+1F⊗F∗)A^p(F)=\operatorname{coker}(\bigwedge^{t-p}F\longrightarrow\bigwedge^{t-p+1}F\otimes F^*). The claim predicts the initial terms of minimal resolutions, generalizing the known Buchsbaum–Eisenbud descriptions; the source presents it as a prediction rather than a proved result.

References

Primary source

Jan O. Kleppe and Rosa M. Miró-Roig, “Schur powers of the cokernel of a graded morphism”, arXiv:2311.08008 (2025).

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