Decomposition criterion for equivalence of spatial graphs

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=Tβ,\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=Tβ,Γ=Tβ,\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.

Sources & referencesView supporting material

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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