The same-degree positive-characteristic intersection-of-orbits conjecture

From papers

Let KK be a field of characteristic pp, and let f,gK[x]f,g\in K[x] be polynomials of the same degree d2d\geq2. Suppose that there exist α,βK\alpha,\beta\in K such that fn(α)=gn(β)f^n(\alpha)=g^n(\beta) for infinitely many nNn\in{\mathbb N}. A polynomial is additive if it satisfies h(x+y)=h(x)+h(y)h(x+y)=h(x)+h(y), and a polynomial is linearly conjugate to hh if it has the form λ1hλ\lambda^{-1}\circ h\circ\lambda for a linear polynomial λ\lambda.

Same-degree intersection-of-orbits conjecture. At least one of the following holds: (1) there exists mNm\in{\mathbb N} such that fm=gmf^m=g^m; or (2) there exist linear polynomials λ,μK[x]\lambda,\mu\in\overline{K}[x] and additive polynomials f~,g~K[x]\widetilde f,\widetilde g\in\overline{K}[x] such that

f=λ1f~λ,g=μ1g~μ,f=\lambda^{-1}\circ\widetilde f\circ\lambda,\qquad g=\mu^{-1}\circ\widetilde g\circ\mu,

and there exists mNm\in{\mathbb N} such that

f~mg~m=g~mf~m.\widetilde f^m\circ\widetilde g^m=\widetilde g^m\circ\widetilde f^m.

This is presented as the special case reducing the broader intersection-of-orbits conjecture; the source does not state a resolution of this special case.

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Sources & referencesView supporting material

Primary source

Simone Coccia, Dragos Ghioca, Jungin Lee and Gyeonghyeon Nam, “Intersection of orbits for polynomials in characteristic p”, arXiv:2408.06937 (2024).

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