Published online by Cambridge University Press: 29 September 2021
We compare the Pontryagin duals of fine Selmer groups of two congruent p-adic Galois representations over admissible pro-p, p-adic Lie extensions $K_\infty $ of number fields K. We prove that in several natural settings the
$\pi $-primary submodules of the Pontryagin duals are pseudo-isomorphic over the Iwasawa algebra; if the coranks of the fine Selmer groups are not equal, then we can still prove inequalities between the
$\mu $-invariants. In the special case of a
$\mathbb {Z}_p$-extension
$K_\infty /K$, we also compare the Iwasawa
$\lambda $-invariants of the fine Selmer groups, even in situations where the
$\mu $-invariants are nonzero. Finally, we prove similar results for certain abelian non-p-extensions.