  Let L be a nonunimodular definite lattice. Using a theorem of Elkies we show
that whether L embeds in the standard definite lattice of the same rank is
completely determined by a collection of lattice correction terms, one for each
metabolizing subgroup of the discriminant group. As a topological application
this gives a rephrasing of the obstruction for a rational homology 3-sphere to
bound a rational homology 4-ball coming from Donaldson's theorem on definite
intersection forms of 4-manifolds. Furthermore, from this perspective it is
easy to see that if the obstruction to bounding a rational homology ball coming
from Heegaard Floer correction terms vanishes, then (under some mild
hypotheses) the obstruction from Donaldson's theorem vanishes too.
