Non-abelian cohomology conjecture for parameterized 1+1d gapped systems

Let XX be a sufficiently nice parameter space, such as a CW complex, let C\mathcal{C} be a fusion category, and let M\mathcal{M} be a fixed C\mathcal{C}-module category with corresponding gapped phase TMC\mathcal{T}_{\mathcal{M}}^{\mathcal{C}}. Let FunC(M,M)inv\underline{\operatorname{Fun}}_{\mathcal{C}}(\mathcal{M},\mathcal{M})^{\mathrm{inv}} be the 2-group of invertible objects and morphisms in the category of C\mathcal{C}-module endofunctors of M\mathcal{M}, and let BFunC(M,M)invB\underline{\operatorname{Fun}}_{\mathcal{C}}(\mathcal{M},\mathcal{M})^{\mathrm{inv}} denote its classifying space. The non-abelian cohomology conjecture. XX-parameterized families of 1+1d gapped systems in TMC\mathcal{T}_{\mathcal{M}}^{\mathcal{C}} are classified by

[X,BFunC(M,M)inv][X,B\underline{\operatorname{Fun}}_{\mathcal{C}}(\mathcal{M},\mathcal{M})^{\mathrm{inv}}]

of homotopy classes of maps, equivalently by the non-abelian Čech cohomology

Hˇ1(X,FunC(M,M)inv).\check{\mathrm{H}}^1(X,\underline{\operatorname{Fun}}_{\mathcal{C}}(\mathcal{M},\mathcal{M})^{\mathrm{inv}}).

The conjecture is motivated by the hypothesis that the space of systems in the phase is homotopy equivalent to this classifying space; the paper does not give a general proof.

Sources & referencesView supporting material

Primary source

Kansei Inamura and Shuhei Ohyama, “1+1d SPT phases with fusion category symmetry: interface modes and non-abelian Thouless pump”, arXiv:2408.15960 (2026).

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