Equivariantization and delooping commute for multifusion categories

Let GG be a group. For a multifusion category C\mathcal{C} with a GG-action, write CG\mathcal{C}^G for its equivariantization and Mod(C)\mathbf{Mod}(\mathcal{C}) for its delooping. For a braided multifusion category A\mathcal{A} with a GG-action, write AG\mathcal{A}^G for its equivariantization. The resulting module 2-categories carry their natural structures over 2Rep(G)\mathbf{2Rep}(G). Equivariantization–delooping conjecture. There should be equivalences of module 2-categories over 2Rep(G)\mathbf{2Rep}(G) and of 2Rep(G)\mathbf{2Rep}(G)-module multifusion 2-categories, respectively:

Mod(C)GMod(CG),\mathbf{Mod}(\mathcal{C})^G \simeq \mathbf{Mod}(\mathcal{C}^G),

and

Mod(A)GMod(AG).\mathbf{Mod}(\mathcal{A})^G \simeq \mathbf{Mod}(\mathcal{A}^G).

The claim predicts that equivariantization commutes with delooping in both the multifusion and braided multifusion settings; the surrounding discussion presents the relevant equivariantization and de-equivariantization constructions for fusion 2-categories only as a rough sketch, indicating that the details remain to be established.

Sources & referencesView supporting material

Primary source

Hao Xu, “On Étale Algebras and Bosonic Fusion 2-Categories”, arXiv:2411.13367 (2024).

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