finitely generated Module over a local ring and fibres of a vector space basis as generators
Proposition
Let be a local ring with Residue field
Suppose is a finitely generated
-modules,
the vector space over
(cf. functor from modules to vector spaces for the residue field).
Assume further that generate
as
module, and
are fibres of
.
Then form a generating set
Proof
w.l.o.g. we may assume that form a
-basis
Let be the generated submodule .
Then it remains to show that
consider the sequence of modules
it follows especially that the composition
is surjective, as form a k-basis of
and hence especially a generating set over
using the first isomorphism theorem for modules there exists a diagram
where
and hence an isomorphism
This shows
by second Nakaymas Lemma for Jacobson Radical we conclude that