Characterising 4-tangles through a connectivity property
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Every large k-connected graph-minor induces a k-tangle in its ambient graph. The converse holds for k≤ 3, but fails for k≥ 4. This raises the question whether `k-connected' can be relaxed to obtain a characterisation of k-tangles through highly cohesive graph-minors. We show that this can be achieved for k=4 by proving that internally 4-connected graphs have unique 4-tangles, and that every graph with a 4-tangle τ has an internally 4-connected minor whose unique 4-tangle lifts to τ.
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