Regular homotopy group of immersions (Ex)
The goal of this exercise is to get more feeling for the regular homotopy group of
-immersions in
,
and the intersection/self-intersection form on it. Below are two definitions of it. Both are used in [Wall1999].
Definition 0.1.
In [Lück2001] the group is defined as follows. Elements of
are represented by pointed
-immersions, i.e pairs
with
is an immersion which does not necessarily map the basepoint
to the basepoint
and
is a path from
to
. Two pairs
are considered equivalent if they are pointed homotopic, i.e. if there exists a regular homotopy
between
and
such that
and
are homotopic relative endpoints. The sum of
and
is defined by forming the (class of the) connected sum immersion
along with the (class of the) path
. The action of
is given by mapping
to
where
is a loop at
representing a
.
is described as follows. Choose representavives with
and
transverse. For every double point
with
determine the sign
in the usual way, i.e. by comparing orientations of
and
. The element
is given by the class of the loop 
is a path in
from
to
.
Definition 0.2.
In [Ranicki2002] the group is defined as follows. Elements of
are represented by
with
a
-immersion and
a lift of
to the universal cover of
. Two pairs
are considered equivalent if they are regular homotopy equivalent. The sum is given by connected sum. The action of
is via deck transformations on the lift.
To determine the equivariant intersection of
and
choose
and
to be transverse. For every doublepoint
with
there exists an element
such that
. Define the equivariant index of
and
at
to be
where
is determined by comparing orientations again.
1) Show that the above definitions of
-modules are equivalent.
2) Show that the descriptions of the equivariant intersections of (regular homotopy classes of)
-immersions coincide.
3) Show that the corresponding descriptions of Wall's
-form (the self-intersection form) coincide up to possible conjugation by a fixed element
.