Usher's obstruction-supremum conjecture for ellipsoid embedding functions

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For n≥1n\geq 1, define

Ln,0=n2−1.L_{n,0}=\sqrt{n^2-1}.

Let Ak,nA_{k,n} and A^k,n\hat A_{k,n} be Usher's obstruction classes, let μE,Ln,0\mu_{\mathbf{E},L_{n,0}} denote the obstruction associated to a class E\mathbf{E}, and let accum(Ln,0)\mathrm{accum}(L_{n,0}) be the accumulation point of the infinite staircase for cLn,0c_{L_{n,0}}. Let the center of A0,nA_{0,n} be the left endpoint of the interval under consideration.

Usher's conjecture. Between the center of A0,nA_{0,n} and accum(Ln,0)\mathrm{accum}(L_{n,0}), the function cLn,0c_{L_{n,0}} equals

sup⁡{μE,Ln,0:E is one of the Ak,n or A^k,n}.\sup\{\mu_{\mathbf{E},L_{n,0}}:\mathbf{E}\text{ is one of the }A_{k,n}\text{ or }\hat A_{k,n}\}.

Usher proved that cLn,0c_{L_{n,0}} has an infinite staircase, while this conjecture predicts the complete embedding function up to its accumulation point using the indicated obstruction classes.

References

Primary source

Caden Farley, Tara Holm, Nicki Magill, Jemma Schroder, Morgan Weiler, Zichen Wang and Elizaveta Zabelina, “Four-periodic infinite staircases for four-dimensional polydisks”, arXiv:2210.15069 (2023).

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