Non-isomorphism of rings of integer-coefficient holomorphic functions on disks of varying radius

Jon Bannon, David Feldman

For $\rho \in (0,1]$, let $R(\rho )=\mathbb{Z}[[z]]\cap O(B(0,\rho ))$ denote the ring of power series with integer Taylor coefficients converging on the open disk $B(0,\rho )$. We prove that t…