The first collapsing-function identity for worms and spiders

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Let \uppsi0\uppsi_0 be the ordinal collapsing function and let \cond⊤\cond_{\top} denote the corresponding worm/spider collapsing operation. The first collapsing-function identity. One has

\uppsi0\Upomegaω1=\cond⊤(0\atopwithdelims⟨⟩\Upomegaω1⊤).\uppsi_0{\Upomega^\omega 1}=\cond_{\top}\left({0 \atopwithdelims \langle \rangle{\Upomega^\omega 1}}\top\right).

This identity is presented as a conjecture because the paper concludes with it as a proposed translation between the two notation systems; the supplied context gives no proof or resolution.

References

Primary source

David Fernández-Duque, “Worms and Spiders: Reflection calculi and ordinal notation systems”, arXiv:1605.08867 (2017).

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