Measuring congruences among modular forms over arithmetic rings has good applications
to number theory. In particular, Hida has shown in 2013 that the non-existence of the following
two types of congruences is almost equivalent to the vanishing of the $\mu$-invariants of the
Kubota-Leopoldt $p$-adic $L$-function and the Katz anti-cyclotomic $p$-adic $L$-function:
(1) a congruence mod $p$ between a $p$-adic family of Eisenstein series and a non-CM
cuspidal Hida family; (2) a congruence mod $p$ between a non-CM and a CM cuspidal
Hida family. In this talk, I will explain my attempt to describe congruence modules that
classify such types of congruences, in the case where the Hilbert modular forms are defined
over a real quadratic field of narrow ideal class number one.
Links:
[1] http://www.mpim-bonn.mpg.de/de/taxonomy/term/39
[2] http://www.mpim-bonn.mpg.de/de/node/3444
[3] http://www.mpim-bonn.mpg.de/de/node/7600