arXiv subjects

Adam L. Epstein

Publications and source records attributed to Adam L. Epstein.

4 recordsLinked to original sources

arXiv2018

Rational maps with a preperiodic critical point

We show that the set of conjugacy classes of cubic polynomials with a prefixed critical point, of preperiod $k\geq 1$, is an irreducible algebraic curve. We also establish an analogous result for quadratic rational maps. We then study a closely related question concerning the irreducibility (over $\mathbb Q$) of the set of conjugacy classes of unicritical polynomials, of degree $D\geq 2$, with a preperiodic critical point. Our proofs are purely algebraic.

math.DS↗

arXiv2017

Eigenvalues of the Thurston operator

Let $f:\hat{\mathbb C}\to \hat{\mathbb C}$ be a postcritically finite rational map. Let $\mathcal Q(\hat{\mathbb C})$ be the space of meromorphic quadratic differentials on $ \hat{\mathbb C}$ with simple poles. We study the set of eigenvalues of the pushforward operator $f_*:\mathcal Q(\hat{\mathbb C})\to \mathcal Q(\hat{\mathbb C})$. In particular, we show that when $f:\mathbb C \to \mathbb C$ is a unicritical polynomial of degree $D$ with periodic critical point, the eigenvalues of $f_*:\mathcal Q(\hat{\mathbb C})\to \mathcal Q(\hat{\mathbb C})$ are contained in the annulus $\bigl\{\frac{1}{4D}<|\lambda|<1\bigr\}$ and belong to $\frac{1}{D} \mathbb U$ where $\mathbb U$ is the group of algebraic units.

math.DS↗

arXiv1997

Bounded hyperbolic components of quadratic rational maps

Let ${\cal H}$ be a hyperbolic component of quadratic rational maps possessing two distinct attracting cycles. We show that ${\cal H}$ has compact closure in moduli space if and only if neither attractor is a fixed point.

math.DS↗

arXiv1996

Geography of the cubic connectedness locus I: Intertwining surgery

We exhibit products of Mandelbrot sets in the two-dimensional complex parameter space of cubic polynomials. These products were observed by J. Milnor in computer experiments which inspired Lavaurs' proof of non local-connectivity for the cubic connectedness locus. Cubic polynomials in such a product may be renormalized to produce a pair of quadratic maps. The inverse construction is an {\it intertwining surgery} on two quadratics. The idea of intertwining first appeared in a collection of problems edited by Bielefeld. Using quasiconformal surgery techniques of Branner and Douady, we show that any two quadratics may be intertwined to obtain a cubic polynomial. The proof of continuity in our two-parameter setting requires further considerations involving ray combinatorics and a pullback argument.

math.DS↗