.
Corollary
Let
be a finite action and let
denote a
transversal of the conjugacy classes of G. Then
Here is the faster version of the Cauchy-Frobenius Lemma.
Another formulation of the Cauchy-Frobenius Lemma makes use of the
permutation representation defined by the action
in question. (Actually in all our programs we apply this version of the Lemma.)
The permutation group
which is the image of
under this representation, yields the action
of
on
,
which has the
same orbits, and so
we also have:
where
.
Corollary
If
denotes a finite
-set, then (for
any group
) the following identity holds:
denotes a transversal of the conjugacy classes of
.
Exercises
E .
Let
be finite and transitive. Consider an
arbitrary
and prove that