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DTSTAMP;TZID=America/Vancouver:20221208T103000
DTSTART;TZID=America/Vancouver:20221208T103000
DTEND;TZID=America/Vancouver:20221208T112000

UID:20221208T103000@prima2022.primamath.org
SUMMARY:Dependence relation among values of canonical heights
DESCRIPTION:Let $d\geq 2$ and let $H$ denote the absolute multiplicative Weil height
on $\bar{\mathbb{Q}}$. Let $f(z)\in \bar{\mathbb{Q}}[z]$ of degree $d$ and
let $a\in\bar{\mathbb{Q}}$, the multiplicative and logarithmic canonical heights
of $a$ with respect to $f$ are defined as

$$
\hat{H}_f (a) =\lim H(f^n(a))^{1/d^n} \quad \text{and}\quad \hat{h}_f(a)=\log \hat{H}_f(a).
$$

Let $n$ be a positive integer. For $1\leq i\leq n$, let
$f_i\in\bar{\mathbb{Q}}[z]$ of degree $d$ and let $a_i\in\bar{\mathbb{Q}}$.
In this talk, we provide a complete characterization of when the
$\hat{H}_{f_i}(a_i)$'s are multiplicatively dependent modulo constant meaning
there exist integers $m_1,\ldots,m_n$ not all of which are $0$ and $a\in
\bar{\mathbb{Q}}$ such that:

$$
\hat{H}_{f_1}(a_1)^{m_1} \cdots \hat{H}\_{f_n}(a_n)^{m_n}=a.
$$

As an immediate consequence, we characterize all the pairs $(f,a)$ such that
$\hat{H}_f(a)$ is an algebraic number and proves the existence of $(f,a)$ such
that $\hat{h}_f(a)$ is an irrational number.  The proof uses the
Medvedev-Scanlon classification of preperiodic subvarieties under the dynamics
of a split polynomial map and the construction of a certain auxiliary
polynomial. This is joint work with Jason Bell.
STATUS:CONFIRMED
LOCATION:Port Alberni
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