English

A disconnected deformation space of rational maps

Dynamical Systems 2016-02-25 v1

Abstract

Let f:(P1,P)(P1,P)f:(\mathbb{P}^1,P)\to(\mathbb{P}^1,P) be a postcritically finite rational map with postcritical set PP. William Thurston showed that ff induces a holomorphic pullback map σf:TPTP\sigma_f:\mathcal{T}_P\to\mathcal{T}_P on the Teichm\"uller space TP:=Teich(P1,P){\mathcal T}_P:=\mathrm{Teich}(\mathbb{P}^1,P). If ff is not a flexible Latt\`es map, Thurston proved that σf\sigma_f has a unique fixed point. In his PhD thesis, Adam Epstein generalized Thurston's ideas and defined a deformation space associated to a rational map f:(P1,A)(P1,B)f:(\mathbb{P}^1,A)\to (\mathbb{P}^1,B) where ABA \subseteq B, allowing for maps ff which are not necessarily postcritically finite. By definition, the deformation space DefBA(f)TB\mathrm{Def}_B^A(f)\subseteq \mathcal{T}_B is the locus where the pullback map σf:TBTA\sigma_f:\mathcal{T}_B\to\mathcal{T}_A and the forgetful map σAB:TBTA\sigma_A^B:\mathcal{T}_B\to\mathcal{T}_A agree. Using purely local arguments, Epstein showed that DefBA(f)\mathrm{Def}_B^A(f) is a smooth analytic submanifold of TB\mathcal{T}_B of dimension BA|B-A|. In this article, we investigate the question of whether DefBA(f)\mathrm{Def}_B^A(f) is connected. We exhibit a family of quadratic rational maps for which the associated deformation spaces are disconnected; in fact, each has infinitely many components.

Keywords

Cite

@article{arxiv.1602.07378,
  title  = {A disconnected deformation space of rational maps},
  author = {Eriko Hironaka and Sarah Koch},
  journal= {arXiv preprint arXiv:1602.07378},
  year   = {2016}
}
R2 v1 2026-06-22T12:56:30.745Z