Finite-cohomology generation conjecture for homotopy categories of injectives

Let GG be a finite group and let k\mathsf{k} be a field of characteristic pp. Let KInj(kG)\mathsf{KInj}(\mathsf{k}G) be the homotopy category of complexes of injective kG\mathsf{k}G-modules. Let KInjb(kG)\mathsf{KInj}^{b}(\mathsf{k}G) be the thick subcategory of objects XX for which H(G,X)H^*(G,X) is finitely generated over H(G,k)H^*(G,\mathsf{k}), and let KInj0(kG)\mathsf{KInj}^{0}(\mathsf{k}G) be the localising subcategory of objects with H(G,X)=0H^*(G,X)=0. The bounded derived category Db(kG)\mathsf{D}^{b}(\mathsf{k}G) is identified with the compact objects in KInj(kG)\mathsf{KInj}(\mathsf{k}G).

Finite-cohomology generation conjecture.

KInjb(kG)=Thick(Db(kG),KInj0(kG)).\mathsf{KInj}^{b}(\mathsf{k}G)=\mathsf{Thick}(\mathsf{D}^{b}(\mathsf{k}G),\mathsf{KInj}^{0}(\mathsf{k}G)).

Thus every object with finitely generated cohomology should be generated by bounded-derived objects and no-cohomology objects. The paper proves this conjecture is equivalent to the corresponding stable-module-category conjecture and records that the general weaker conjecture remains open.

Sources & referencesView supporting material

Primary source

David J. Benson and John Greenlees, “Modules with finitely generated cohomology, and singularities of C^*BG”, arXiv:2305.08580 (2023).

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