9.2 Sectors in the space of Dolbeault forms
Let be holomorphic vector bundles as above.
There is an analog of the dg-category in the case
of complex numbers. We will denote it by . Objects
of are holomorphic vector bundles on of the type
. Morphisms are sections of soft sheaves on .
Namely, we define the sheaf
on as the direct image
(in the self-explained notation). Then
are global sections of this sheaf.
This sheaf corresponds to the sheaf
in the non-archimedean geometry.
Let us choose an open affine chart .
Then
contains a subsheaf of finite Fourier sums with respect
to the natural action of the torus
on
.
Thus we have the sheaf
which is an analog of the sheaf
considered in the non-archimedean case.
Notice that there exists a natural homomorphism of sheaves
.
The image of consists of Dolbeault forms on which have
coefficients locally constant along fibers of .
In local coordinates is given by the formula
,
where .
It is easy to see that is compatible with the structure
of dg-algebras on de Rham and Dolbeault forms.
Thus for a pair of holomorphic vector bundles and on
we have a canonical structure of dg-module over
on the sheaf
.
In the case when the subsheaf
is also a sheaf of dg-modules over .
As in the non-archimedean case there is a canonical decomposition
of the stalk
into the direct sum of dg-modules of finite rank over
. Summands are labeled by
the homotopy classes and
called sectors. We will denote them by
.
Informally, sectors correspond to βFourier componentsβ
of Dolbeault forms in
in the direction of torus fibers.
Let us describe them more explicitly. For simplicity we will
assume that are rank one trivial local systems,
and intersect with each fiber of at exactly
one point. Then near we can write
, where
are germs at of smooth functions on .
ΒΏFrom the description of the PoincarΓ© bundle we deduce
that
is canonically identified with the space of germs
of -forms near ,
endowed with the twisted differential
,
where .
Then the sector corresponding to a path consists
of Dolbeault forms
.
Here vector is the homotopy class of the loop
in which is the composition of three paths:
1) the path ;
3) the path .
A choice of sector corresponds to the choice
of monomial in the non-archimedean case.
Homotopy classes of paths in non-archimedean approach correspond
the summands of Fourier series.
Locally each sector can be identified with the de Rham complex
on . Namely, to a form
we assign the form , where defines the sector.
It is easy to see that
the differential on
Dolbeault forms on corresponds to the de Rham differential
on .
In this way we obtain an isomorphism of complexes
.
Remark 21
When is not a fixed number,
but a parameter ,
the coefficients are asymptotic series
in of the type
where ,
, and .
The set of exponents appearing in the expansion of at
corresponds to the spectrum considered
in the non-archimedean case.