Let $E$ and $E'$ be elliptic curves over an algebraic number field. We show that systems of $\ell$-adic representations associated with $E$ and $E'$ are cohomologically coprime, in the sense that the Galois cohomology groups corresponding to respective fields of division points are all trivial. This provides a generalization of some known results about the vanishing of the cohomology groups associated with the $\ell$-adic Tate module of an elliptic curve.

In connection with Nevanlinna’s five-value theorem ([2]), the author showed in~[3] that two meromorphic functions sharing five one-point or two-point sets IM are Möbius transforms of each other. Now, we consider $n+1$ meromorphic functions sharing some finite sets IM.

In this paper, we give a rigidity theorem for holomorphic disks associated to holomorphic families of Riemann surfaces, aiming for studying the geometry (the asymptotic boundary behaviors) of such holomorphic disks. Indeed, our rigidity theorem is described with distributions of associated holomorphic disks and orbits of monodromies at infinity.

We study the set $\mathcal{G}$ of growth rates of ideal Coxeter groups in hyperbolic 3-space; this set consists of real algebraic integers greater than 1. We show that (1) $\mathcal{G}$ is unbounded above while it has the minimum, (2) any element of $\mathcal{G}$ is a Perron number, and (3) growth rates of ideal Coxeter groups with $n$ generators are located in the closed interval $[n-3, n-1]$.

A result of Malyutin shows that a random walk on the mapping class group gives rise to an element whose fractional Dehn twist coefficient is large or small enough. We show that this leads to several properties of random 3-manifolds and links. For example, random closed braids and open books are hyperbolic.