The continued-fraction length conjecture for staircase classes

Let Eδ{\bf E}_{\delta} be a class with center p/qp/q, and let CS(Eδ)\ell_{{\mathcal C}{\mathcal S}}({\bf E}_{\delta}) denote its CS{\mathcal C}{\mathcal S}-length. Let CFCF-length denote the length of a continued-fraction expansion, and consider the two staircases associated to Eδ{\bf E}_{\delta}.

Continued-fraction length conjecture. (i) The continued-fraction expansion of the center p/qp/q of Eδ{\bf E}_{\delta} has CFCF-length CS(Eδ)\ell_{{\mathcal C}{\mathcal S}}({\bf E}_{\delta}). (ii) The steps of the two staircases associated to Eδ{\bf E}_{\delta} have periodic continued fractions with periodic part of length 2CS(Eδ)2\ell_{{\mathcal C}{\mathcal S}}({\bf E}_{\delta}). Moreover, these periodic parts have reverse cyclic order.

The conjecture predicts a precise correspondence between recursively defined combinatorial lengths of staircase classes and the arithmetic structure of their centers and steps. No resolution is given in the supplied text.

Sources & referencesView supporting material

Primary source

Nicki Magill, Dusa McDuff and Morgan Weiler, “Staircase Patterns in Hirzebruch Surfaces”, arXiv:2203.06453 (2023).

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