The $μ$-invariant change for abelian varieties over finite $p$-extensions of global fields

Ki-Seng Tan, Fabien Trihan, Kwok-Wing Tsoi

Published 2023-01-22Version 1

We extend the work of Lai, Longhi, Suzuki, the first two authors and study the change of $\mu$-invariants, with respect to a finite Galois p-extension $K'/K$, of an ordinary abelian variety $A$ over a $\mathbb{Z}_p^d$-extension of global fields $L/K$ (whose characteristic is not necessarily positive) that ramifies at a finite number of places at which $A$ has ordinary reductions. We obtain a lower bound for the $\mu$-invariant of $A$ along $LK'/K'$ and deduce that the $\mu$-invariant of an abelian variety over a global field can be chosen as big as needed. Finally, in the case of elliptic curve over a global function field that has semi-stable reduction everywhere we are able to improve the lower bound in terms of invariants that arise from the supersingular places of $A$ and certain places that split completely over $L/K$.