arXiv subjects

Su-Ion Ih

Publications and source records attributed to Su-Ion Ih.

4 recordsLinked to original sources

arXiv2020

A finiteness property of postcritically finite unicritical polynomials

Let $k$ be a number field with algebraic closure $\bar{k}$, and let $S$ be a finite set of places of $k$ containing all the archimedean ones. Fix $d\geq 2$ and $α\in \bar{k}$ such that the map $z\mapsto z^d+α$ is not postcritically finite. Assuming a technical hypothesis on $α$, we prove that there are only finitely many parameters $c\in\bar{k}$ for which $z\mapsto z^d+c$ is postcritically finite and for which $c$ is $S$-integral relative to $(α)$. That is, in the moduli space of unicritical polynomials of degree d, there are only finitely many PCF $\bar{k}$-rational points that are $((α),S)$-integral. We conjecture that the same statement is true without the technical hypothesis.

math.NT↗

arXiv2020

Discreteness of postcritically finite maps in p-adic moduli space

Let $p \geq 2$ be a prime number and let $\mathbb{C}_p$ be the completion of an algebraic closure of the $p$-adic rational field $\mathbb{Q}_p$. Let $f_c(z)$ be a one-parameter family of rational functions of degree $d\geq 2$, where the coefficients are meromorphic functions defined at all parameters $c$ in some open disk $D\subseteq\mathbb{C}_p$. Assuming an appropriate stability condition, we prove that the parameters $c$ for which $f_c$ is postcritically finite (PCF) are isolated from one another in the $p$-adic disk $D$, except in certain trivial cases. In particular, all PCF parameters of the family $f_c(z)=z^d+c$ are $p$-adically isolated.

math.NT↗

arXiv2008

A finiteness property for preperiodic points of Chebyshev polynomials

Let K be a number field with algebraic closure K-bar, let S be a finite set of places of K containing the archimedean places, and let f be a Chebyshev polynomial. We prove that if a in K-bar is not preperiodic, then there are only finitely many preperiodic points b in K-bar which are S-integral with respect to a.

math.NT↗

arXiv2005

A finiteness property of torsion points

Let k be a number field, let E/k be an elliptic curve, and let S be a finite set of places of k contianing the archimedean places. Let F be an algebraic closure of k. We prove that if a point P in E(F) is nontorsion, then there are only finitely many torsion points x in E(F) which are S-integral with respect to P. We also prove an analogue of this for the multiplicative group, and formulate conjectural generalizations for abelian varieties and dynamical systems.

math.NT↗