Jones's index conjecture for quadratic rational maps

Let KK be a global field, let fK(x)f\in K(x) have degree two, and let TT_\infty be the infinite rooted binary tree of preimages of a root α\alpha under ff. Write G(f,α)G_\infty(f,\alpha) for the image of the associated arboreal Galois representation. Jones's conjecture. One has

[Aut(T):G(f,α)]=[\operatorname{Aut}(T_\infty):G_\infty(f,\alpha)]=\infty

if and only if at least one of the following holds: ff is postcritically finite; the two critical points γ1\gamma_1 and γ2\gamma_2 satisfy fr+1(γ1)=fr+1(γ2)f^{r+1}(\gamma_1)=f^{r+1}(\gamma_2) for some r1r\geq 1; the root α\alpha is periodic under ff; or a nontrivial Möbius transformation commuting with ff fixes α\alpha. This gives criteria for when the arboreal image has infinite index in the full automorphism group; the supplied text does not indicate whether the conjecture has been resolved.

Sources & referencesView supporting material

Primary source

Jamie Juul, Holly Krieger, Nicole Looper, Michelle Manes, Bianca Thompson and Laura Walton, “Arboreal representations for rational maps with few critical points”, arXiv:1804.06053 (2018).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.