Decomposition criterion for equivalence of spatial graphs

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Let Γ\Gamma and Γ′\Gamma' be finite spatial graphs corresponding to the same combinatorial graph G\mathcal{G}. A forest–tangle decomposition is a decomposition of a spatial graph as a connected sum

Γ=T‾♯β‾,\Gamma=\overline{T}\mathbin{\sharp}\overline{\beta},

where T‾\overline{T} is a forest and β‾\overline{\beta} is a tangle.

Decomposition criterion. The graphs Γ\Gamma and Γ′\Gamma' are equivalent if and only if they admit decompositions

Γ=T‾♯β‾,Γ′=T′‾♯β′‾,\Gamma=\overline{T}\mathbin{\sharp}\overline{\beta},\qquad \Gamma'=\overline{T'}\mathbin{\sharp}\overline{\beta'},

where T‾\overline{T} is equivalent to T′‾\overline{T'} as spatial graphs and β‾\overline{\beta} is equivalent to β′‾\overline{\beta'} as tangles.

This criterion would separate equivalence of spatial graphs into the equivalence of their forest and tangle components, addressing the nonuniqueness of the decomposition arising from the choice of a maximal forest. The supplied text does not establish the claim or indicate whether it has been proved or disproved.

References

Primary source

Valeriy G. Bardakov and Akio Kawauchi, “Spatial graph as connected sum of a planar graph and a braid”, arXiv:2006.16072 (2020).

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