Fixed-point lifting and ghost periodic points for Chebyshev polynomials modulo odd prime powers
Abstract
Let be an odd prime, let , and let the th Chebyshev polynomial act on . We count fixed and exact-periodic points, allowing non-permutation degrees, and organize the finite-field formulas by the two source groups needed for prime-power lifting. Over we record the four-GCD fixed-point formula where . The proof separates split and nonsplit source groups for and counts degenerate fixed residues branch-wise. For every odd , Here denotes the number of fixed residue classes for which . For and all , This all-level formula does not extend unchanged to , where boundary -adic estimates at can fail; the first-lift formula remains valid. For periods, we use the Chebyshev order A source-order- point is periodic over exactly when , with period . M\"obius inversion for the iterates gives exact-period point counts over for all odd ; for , the all-level fixed-point formula gives closed forms. When , orbitwise lifting modulo gives either full period retention or one Hensel lift plus ghost periodic points of period . For , higher lifts above a periodic residue are governed by the tower .
Cite
@article{arxiv.2605.04417,
title = {Fixed-point lifting and ghost periodic points for Chebyshev polynomials modulo odd prime powers},
author = {Chatchawan Panraksa and Aram Tangboonduangjit},
journal= {arXiv preprint arXiv:2605.04417},
year = {2026}
}
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36 pages