Uniform critical-orbit comparison for bi-critical irrationally indifferent attractors

Let ff be a rational map with a bi-critical irrationally indifferent attractor at 00. For each active critical point cc, let β\beta denote the angle from cc to the other critical point, and let \mathdsTα,β\mathds{T}_{\alpha,\beta} be the associated model map.

Uniform critical-orbit comparison conjecture. There exists a uniform constant C>0C_{}>0 such that, for all k0k\geq 0,

C1\mathdsTα,βk(+1)fk(c)C\mathdsTα,βk(+1).C_{}^{-1} \left|\mathds{T}_{\alpha,\beta}^{\circ k}(+1)\right| \leq \left|f^{\circ k}(c)\right| \leq C_{}\left|\mathds{T}_{\alpha,\beta}^{\circ k}(+1)\right|.

This conjecture predicts that the orbit of each active critical point has, up to a uniform multiplicative constant, the same scale as the corresponding arithmetic-geometric model orbit. The surrounding discussion relates this expected comparison to the geometric similarities between bi-critical and uni-critical near-parabolic renormalisation models; partial progress is known for multi-critical renormalisation, but the stated uniform estimate is not resolved here.

Sources & referencesView supporting material

Primary source

Jocelyn Finbar Russell, “Arithmetic Geometric Model for the Renormalisation of Bi-critical Irrationally Indifferent Attractors”, arXiv:2511.04656 (2026).

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