Difference between revisions of "Moduli spaces of pseudoholomorphic polygons"
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On the other hand, any J-holomorphic map <math>u:\R\times[0,1]\to M</math> has nonnegative energy density <math>u^*\omega= \bigl(|\partial_s u|^2+|\partial_t u|^2\bigr) ds\wedge dt</math> with <math>|\partial_s u|=|\partial_t u|</math>. | On the other hand, any J-holomorphic map <math>u:\R\times[0,1]\to M</math> has nonnegative energy density <math>u^*\omega= \bigl(|\partial_s u|^2+|\partial_t u|^2\bigr) ds\wedge dt</math> with <math>|\partial_s u|=|\partial_t u|</math>. | ||
If we now had nontrivial isotropy, i.e. <math>u(\tau+s,t)=u(s,t)</math> for some <math>\tau>0</math> and a nonconstant map <math>u</math>, then there would exist <math>s_0,t_0\in \R\times[0,1]</math> with <math>|\partial_s u(s_0,t_0)|=|\partial_t u(s_0,t_0)|>0</math> and thus | If we now had nontrivial isotropy, i.e. <math>u(\tau+s,t)=u(s,t)</math> for some <math>\tau>0</math> and a nonconstant map <math>u</math>, then there would exist <math>s_0,t_0\in \R\times[0,1]</math> with <math>|\partial_s u(s_0,t_0)|=|\partial_t u(s_0,t_0)|>0</math> and thus | ||
− | <math>\int_{[s_0 - \frac{1}{2} \tau]\times[0,1]}^{[s_0 + \frac{1}{2} \tau]\times[0,1]} u^*\omega > 0</math>. | + | <math>\textstyle\int_{[s_0 - \frac{1}{2} \tau]\times[0,1]}^{[s_0 + \frac{1}{2} \tau]\times[0,1]} u^*\omega > 0</math>. |
However, this is in contradiction to <math>u</math> having finite energy, | However, this is in contradiction to <math>u</math> having finite energy, | ||
<center> | <center> |
Revision as of 14:22, 27 May 2017
To construct the moduli spaces from which the composition maps are defined we fix an auxiliary almost complex structure which is compatible with the symplectic structure in the sense that
defines a metric on
. (Unless otherwise specified, we will use this metric in all following constructions.)
Then given Lagrangians
and generators
of their morphism spaces, we need to specify the (compactified) moduli space
.
We will do this by combining two special cases which we discuss first.
Pseudoholomorphic polygons for pairwise transverse Lagrangians
If each consecutive pair of Lagrangians is transverse, i.e. , then our construction is based on pseudoholomorphic polygons
where is a disk with
boundary punctures in counter-clockwise order
, and
denotes the boundary component between
(resp. between
for i=d).
More precisely, we construct the (uncompactified) moduli spaces of pseudoholomorphic polygons for any tuple
for
as in [Seidel book]:
where
-
is a tuple of pairwise disjoint marked points on the boundary of a disk, in counter-clockwise order.
-
is a smooth map satisfying
- the Cauchy-Riemann equation
,
- Lagrangian boundary conditions
,
- the finite energy condition
,
- the limit conditions
for
.
- the Cauchy-Riemann equation
- The pseudoholomorphic polygon
is stable in the sense that the map
is nonconstant if the number of marked points is
.
Here two pseudoholomorphic polygons are equivalent if there is a disk automorphism
that preserves the complex structure on
, the marked points
, and relates the pseudoholomorphic polygons by reparametrization,
.
The case is not considered in this part of the moduli space setup since
are never transverse. However, it might appear in the construction of homotopy units?
For , the twice punctured disks are all biholomorphic to the strip
, so that we could equivalently set up the moduli spaces
by fixing the domain
and defining the equivalence relation
only in terms of the shift action
of
. This is the only case in which the stability condition is nontrivial: It requires the maps
to be nonconstant.
For , the moduli space of domains

can be compactified to form the Deligne-Mumford space , whose boundary and corner strata can be represented by trees of polygonal domains
with each edge
represented by two punctures
and
. The thin neighbourhoods of these punctures are biholomorphic to half-strips, and a neighbourhood of a tree of polygonal domains is obtained by gluing the domains together at the pairs of strip-like ends represented by the edges.
So far, all isotropy groups of this uncompactified moduli space are trivial; that is any disk automorphism
that fixes
marked points
, and preserves a pseudoholomorphic map
must be the identity
.
In case
this follows directly from the marked points, since any Mobius transformation that fixes three points is the identity.
In case
this requires both the stability and finite energy conditions: The group of automorphisms that fix two marked points - i.e. the automorphisms of the strip - are shifts by
.
On the other hand, any J-holomorphic map
has nonnegative energy density
with
.
If we now had nontrivial isotropy, i.e.
for some
and a nonconstant map
, then there would exist
with
and thus
.
However, this is in contradiction to
having finite energy,
Next, to construct the compactified moduli spaces we have to add various strata to the moduli space of pseudoholomorphic polygons without breaking or nodes
defined above. This is done precisely in the general construction below, but roughly requires to
- include degenerate pseudoholomorphic polygons given by a tuple of pseudoholomorphic maps
whose domain is a nontrivial tree of domains
;
- allow for Floer breaking at each puncture of the domains
, i.e. a finite string of pseudoholomorphic strips in
;
- allow for disk bubbling at any boundary point of the above domains, i.e. a tree, each of whose vertices is represented by a pseudoholomorphic disk, with edges representing nodes - given by marked points on different disks at which the maps satisfy a matching condition;
- allow for sphere bubbling at any (boundary or interior) point of each of the above domains, i.e. a tree, each of whose vertices is represented by a pseudoholomorphic sphere, with edges representing nodes - given by marked points on different spheres at which the maps satisfy a matching condition.
We will see that sphere bubbling does not contribute to the boundary stratification of these moduli spaces, so that the boundary stratification and thus the algebraic structure arising from these moduli spaces is induced by Floer breaking and disk bubbling. (On the other hand, sphere bubbling will be the only source of nontrivial isotropy.)
The boundary strata arising from Floer breaking are fiber products of other moduli spaces of pseudoholomorphic polygons over finite sets of Lagrangian intersection points, which indicates an algebraic composition in this finitely generated Floer chain complex.
Disk bubbling, on the other hand, in the present setting yields boundary strata that are fiber products over the Lagrangian submanifold specified by the boundary condition. The corresponding algebraic composition requires a push-pull construction on some space of chains, currents, or differential forms on the Lagrangian. However, such constructions require transversality of the chains to the evaluation maps from the regularized moduli spaces, so that a rigorous construction of the -structure in this setting - as in the approach by Fukaya et al - requires a complicated infinite iteration.
We will resolve this issue as in [J.Li thesis] by following another earlier proposal by Fukaya-Oh to allow disks to flow apart along a Morse trajectory, thus yielding disk trees which are constructed next - still ignoring sphere bubbling - before we put everything together to a general construction of the compactified moduli space.
Pseudoholomorphic disk trees for a fixed Lagrangian
If the Lagrangians are all the same, , then our construction is based on pseudoholomorphic disks
Such disks (modulo reparametrization by automorphisms of the disk) also arise from compactifying other moduli spaces of pseudoholomorphic curves in which energy concentrates at a boundary point.
To capture this bubbling algebraically, we work throughout with the Morse function chosen in the setup of the morphism space
. We also choose a metric on
so that the gradient vector field
satisfies the Morse-Smale conditions and an additional technical assumption in [1] which guarantees a natural smooth manifold-with-boundary-and-corners structure on the compactified Morse trajectory spaces
for
.
This smooth structure is essentially induced by the requirement that the evaluation maps at positive and negative ends
are smooth.
With that data and the fixed almost complex structure
we can construct the moduli spaces of pseudoholomorphic disk trees for any tuple
as in JL:
where
-
is an ordered tree with the following structure on the sets of vertices
and edges
:
- The edges
are oriented towards the root vertex
of the tree, i.e. for
the outgoing vertex
is still connected to the root after removing
. Thus each vertex
has a unique outgoing edge
(except for the root vertex which has no outgoing edge) and a (possibly empty) set of incoming edges
. Moreover, the set of incoming edges is ordered,
with
denoting the valence - number of attached edges - of
.
- The set of vertices is partitioned
into the sets of main vertices
and the set of critical vertices
. The latter is ordered to start with the root
, which is required to have a single edge
, and then contains d leaves
of the tree (i.e. with
), with order induced by the orientation and order of the edges (with the root being the minimal vertex).
- The edges
-
is a tuple of generalized Morse trajectories in the following compactified Morse trajectory spaces:
-
for any edge
between critical vertices;
for any edge
from a critical vertex
to a main vertex
;
for any edge
from a main vertex
to a critical vertex
;
for any edge
between main vertices
.
-
-
is a tuple of boundary marked points as follows:
- For each main vertex
there are
pairwise disjoint marked points
on the boundary of a disk.
- The order
of the edges corresponds to a counter-clockwise order of the marked points
.
- The marked points can also be denoted as
and
by the edges
for which
or
.
- For each main vertex
- For each main vertex
there is a pseudoholomorphic disk, that is a smooth map
satisfying
- the Cauchy-Riemann equation
,
- Lagrangian boundary conditions
,
- the finite energy condition
.
- The pseudholomorphic disks can also be indexed as
and
by the edges
for which
or
. In that notation, they satisfy the matching conditions with the generalized Morse trajectories
whenever
.
- the Cauchy-Riemann equation
- The disk tree is stable in the sense that any main vertex
whose disk has zero energy
(which is equivalent to
being constant) has valence
.
Finally, two pseudoholomorphic disk trees are equivalent if there is a tree isomorphism
and a tuple of disk automorphisms
preserving the complex structure on
such that
-
preserves the tree structure and order of edges;
- the Morse trajectories are the preserved
for every
;
- the marked points are preserved
for every
and adjacent edge
;
- the pseudoholomorphic disks are related by reparametrization,
for every
.
Any equivalence class of disk trees induces a domain tree
as follows:
- The tree
is obtained from
by replacing critical vertices and their outgoing edges by incoming semi-infinite edges of the new tree
. We also replace the critical root vertex and its incoming edge by an outgoing semi-infinite edge of the new tree
. The new tree
retains the orientations of edges and inherits an order of the edges from
. Its root is the unique main vertex from which there was an edge to the critical root vertex in
.
- Every vertex
of
then represents a disk domain
.
- Every edge
is labeled with the length
of the associated generalized Morse trajectory. For the semi-infinite edges, this length is automatically
since the associated Morse trajectories are semi-infinite.
- The domain for each vertex
is marked by
boundary points
, ordered counter-clockwise.
- Two such trees are equivalent
if there is a tree isomorphism
and a tuple of disk automorphisms
preserving the complex structure on
such that
preserves the ordered tree structure and lengths
for every
, and the marked points are preserved
for every
and adjacent
.
For , such a domain tree is called stable if every vertex has valence
- i.e. there are at least three marked points on each disk
.
The domain trees for
are never stable, but both cases need to be included in our moduli space constructions:
The differential
on the Floer chain complex
is constructed by counting the elements of
.
The curvature term
, which is constructed from moduli spaces
with no incoming critical points, serves to algebraically encode disk bubbling in any moduli space involving a Lagrangian boundary condition on
.
For , while the above trees are not necessarily stable, they induce unique stable rooted metric ribbon trees
in the sense of [Def.2.7, MW], by forgetting the marked points, forgetting every leaf of valence 1 and its outgoing edge, and replacing every vertex
of valence 2 and its incoming and outgoing edges
by a single edge
of length
. The space of such stable rooted metric ribbon trees - where a tree containing an edge of length
is identified with the tree in which this edge and its adjacent vertices are replaced by a single vertex - is another topological representation of the Deligne Mumford space
, as discussed in [BV].
Its boundary strata are given by trees with interior edges of length
.
Similarly, we expect the boundary stratification of the moduli spaces of disk trees - if/once regular - to arise exclusively from breaking of the Morse trajectories representing edges of the disk trees. This is made rigorous in [J.Li thesis] under the assumption that the almost complex structure
can be chosen such that there exist no nonconstant
-holomorphic spheres in the symplectic manifold
.
In that special case, all isotropy groups are trivial by [Prop.2.5, J.Li thesis]; that is any equivalence between a disk tree and itself,
, is given by the trivial tree isomorphism
, and the only disk automorphisms
which preserve the marked points and pseudoholomorphic disk maps are the identity maps
.
In this case, the moduli spaces of disk trees
are moreover compact since sphere bubbling is ruled out and disk bubbling is captured by edges labeled with constant, zero length, Morse trajectories.
In general, we will compactify in the following general construction by allowing for sphere bubble trees developing at any (boundary or interior) point of each of the disk domains. This will also be a source of generally nontrivial isotropy.
General moduli space of pseudoholomorphic polygons
Given Lagrangians
and generators
of their morphism spaces, we construct the (compactified) moduli space of pseudoholomorphic polygons by combining the two special cases above:
where
-
is an ordered tree with the following structure on the sets of vertices
and edges
:
- The edges
are oriented towards the root vertex
of the tree, so that each vertex
has a unique outgoing edge
(except for the root vertex which has no outgoing edge) and a (possibly empty) set of incoming edges
. Moreover, the set of incoming edges is ordered,
.
- The set of vertices is partitioned
into the sets of polygon vertices
, disk vertices
, and critical vertices
. The latter is ordered to start with the root
, which is required to have a single edge
, and then contains d leaves
of the tree, with order induced by the orientation and order of the edges.
- The edges
-
is a tuple of boundary points as follows:
- For each polygon or disk vertex
there are
pairwise disjoint marked points
on the boundary of a disk.
- The order
of the edges corresponds to a counter-clockwise order of the marked points
.
- In particular, the marked points
for a polygon vertex
partition the boundary of
into
connected components
such that the closure of each component
contains the marked points
and
. (Here we enumerate the edges adjacent to
cyclically, i.e. denote
.)
- For each polygon or disk vertex
-
is a tuple of Lagrangian labels as follows:
- For each disk vertex
the Lagrangian label
is a single Lagrangian (which will become the boundary condition on
).
- For each polygon vertex
the Lagrangians label
is a sequence of Lagrangians
(which will become the boundary condition on
)
- For each disk vertex
- The order
of the edges corresponds to a counter-clockwise order of the marked points
.
- The order
-
is a tuple of generalized Morse trajectories in the following compactified Morse trajectory spaces:
-
for any edge
between critical vertices;
for any edge
from a critical vertex
to a disk vertex
;
for any edge
from a disk vertex
to a critical vertex
;
for any edge
between disk vertices
or a mixture of disk and polygon vertices
-
;
is a constant Morse trajectory in a discrete space for any edge
between polygon vertices
or a mixture of disk and polygon vertices
;
- The marked points can also be denoted as
and
by the edges
for which
or
.
- The marked points can also be denoted as
- For each main vertex
there is a pseudoholomorphic disk, that is a smooth map
satisfying
- the Cauchy-Riemann equation
,
- Lagrangian boundary conditions
,
- the finite energy condition
.
- The pseudholomorphic disks can also be indexed as
and
by the edges
for which
or
. In that notation, they satisfy the matching conditions with the generalized Morse trajectories
whenever
.
- the Cauchy-Riemann equation
- The disk tree is stable in the sense that any main vertex
whose disk has zero energy
(which is equivalent to
being constant) has valence
.
Here two pseudoholomorphic polygons are equivalent if
Make up for differences in Hamiltonian symplectomorphisms applied to each Lagrangian by a domain-dependent Hamiltonian perturbation to the Cauchy-Riemann equation
Finally, the symplectic area function in each case is given by TODO
Fredholm index