The nonexistence of a skein theory for the tangle group functor

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Let Tang\mathcal{T}ang be the category of tangles, let ΛGrp\Lambda\mathbf{Grp} be the category of groups, and let Γ ⁣:Tang→ΛGrp\Gamma\colon\mathcal{T}ang\to\Lambda\mathbf{Grp} be the tangle group functor. A skein theory for Γ\Gamma is a finitely generated tensor ideal I\mathcal{I} of Tang\mathcal{T}ang such that Γ\Gamma factors through the canonical projection to Tang/I\mathcal{T}ang/\mathcal{I}; write the induced functor as Γ~ ⁣:Tang/I→ΛGrp\tilde{\Gamma}\colon\mathcal{T}ang/\mathcal{I}\to\Lambda\mathbf{Grp}. Nonexistence conjecture. There is no skein theory for Γ\Gamma: no finitely generated tensor ideal I\mathcal{I} of Tang\mathcal{T}ang has both the property that Γ\Gamma factors through Tang/I\mathcal{T}ang/\mathcal{I} and the property that Γ~\tilde{\Gamma} is injective. The claim says that the tangle group functor cannot be localized by finitely many tensor-ideal relations while retaining injectivity on the resulting quotient. The supplied text gives no evidence of resolution, so the conjecture is recorded as open.

References

Primary source

John Armstrong, “The Extension of Knot Groups to Tangles”, arXiv:math/0509665 (2005).

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