Ji's length-spectrum rigidity conjecture for rational maps

Let ff and gg be non-Lattès rational maps of degree d2d\geq 2. For each n1n\geq 1, let Ln(f)L_n(f) denote the unordered collection of absolute derivatives at the fixed points of fnf^n, and let the length spectrum be the sequence (Ln(f))n1(L_n(f))_{n\geq 1}. Let τd(f)\tau_d(f) denote the multiplier-spectrum invariant introduced in the source, and let g\overline g be the complex conjugate of gg.

Length-spectrum rigidity conjecture. If ff and gg have the same length spectrum, then

τd(f)=τd(g)orτd(f)=τd(g).\tau_d(f)=\tau_d(g)\quad\text{or}\quad \tau_d(f)=\tau_d(\overline g).

The conjecture gives a precise description of rational maps with identical length spectra. It is presented as a conjecture proposed by Ji and the author; no resolution is supplied in the passage.

Sources & referencesView supporting material

Primary source

Junyi Xie, “Rigidity in Complex Dynamics: Multiplier Spectrum and Dynamical André-Oort Conjecture”, arXiv:2511.12111 (2025).

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