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

Jon Bannon, David Feldman

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