Vanishing of the cotangent cohomology for flag combinatorial spheres

Let K\mathcal{K} be a combinatorial sphere and a flag complex. For every codimension-22 face ff, let lk(f,K)\operatorname{lk}(f,\mathcal{K}) denote its link, and let AKA_{\mathcal{K}} be the Stanley–Reisner ring of K\mathcal{K}.

Vanishing conjecture. If lk(f,K)\operatorname{lk}(f,\mathcal{K}) is a 44-gon or a 55-gon for every codimension-22 face ff, then

TAK2=0.T^2_{A_{\mathcal{K}}}=0.

The conjecture is motivated by computations for flag 33-spheres obtained by successive edge starrings, as well as by the corresponding result in dimension 22. The stated computations found trivial T2T^2 in all 7474 examples considered, but the general assertion remains open.

Sources & referencesView supporting material

Primary source

Jan Arthur Christophersen and Nathan Owen Ilten, “Degenerations to Unobstructed Fano Stanley-Reisner Schemes”, arXiv:1102.4521 (2012).

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