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Katrin Wehrheim

Publications and source records attributed to Katrin Wehrheim.

32 records · Page 2Linked to original sources

Pseudoholomorphic Quilts

We define relative Floer theoretic invariants arising from 'quilted pseudo-holomorphic surfaces': Collections of pseudoholomorphic maps to various target spaces with 'seam conditions' in Lagrangian correspondences. As application we construct a morphism on quantum homology associated to any monotone Lagrangian correspondence.

math.SG↗

Quilted Floer trajectories with constant components

We fill a gap in the proof of the transversality result for quilted Floer trajectories in arXiv:0905.1370 by addressing trajectories for which some but not all components are constant. Namely we show that for generic sets of split Hamiltonian perturbations and split almost complex structures, the moduli spaces of parametrized quilted Floer trajectories of a given index are smooth of expected dimension. An additional benefit of the generic split Hamiltonian perturbations is that they perturb the given cyclic Lagrangian correspondence such that any geometric composition of its factors is transverse and hence immersed.

math.SG↗

Functoriality for Lagrangian correspondences in Floer theory

Using quilted Floer cohomology and relative quilt invariants, we define a composition functor for categories of Lagrangian correspondences in monotone and exact symplectic Floer theory. We show that this functor agrees with geometric composition in the case that the composition is smooth and embedded. As a consequence we obtain 'categorification commutes with composition' for Lagrangian correspondences.

math.SG↗

Quilted Floer Cohomology

We generalize Lagrangian Floer cohomology to sequences of Lagrangian correspondences. For sequences related by the geometric composition of Lagrangian correspondences we establish an isomorphism of the Floer cohomologies. We give applications to calculations of Floer cohomology, displaceability of Lagrangian correspondences, and transfer of displaceability under geometric composition.

math.SG↗

$L^2$-topology and Lagrangians in the space of connections over a Riemann surface

We examine the $L^2$-topology of the gauge orbits over a closed Riemann surface. We prove a subtle local slice theorem based on the div-curl Lemma of harmonic analysis, and deduce local pathwise connectedness and local uniform quasiconvexity of the gauge orbits. Using these, we generalize compactness results for anti-self-dual instantons with Lagrangian boundary counditions to general gauge invariant Lagrangian submanifolds. This provides the foundation for the construction of instanton Floer homology for pairs of a $3$-manifold with boundary and a Lagrangian in the configuration space over the boundary.

math.GT↗

Instanton Floer homology with Lagrangian boundary conditions

In this paper we define instanton Floer homology groups for a pair consisting of a compact oriented 3-manifold with boundary and a Lagrangian submanifold of the moduli space of flat SU(2)-connections over the boundary. We carry out the construction for a general class of irreducible, monotone boundary conditions. The main examples of such Lagrangian submanifolds are induced from a disjoint union of handle bodies such that the union of the 3-manifold and the handle bodies is an integral homology 3-sphere. The motivation for introducing these invariants arises from our program for a proof of the Atiyah-Floer conjecture for Heegaard splittings. We expect that our Floer homology groups are isomorphic to the usual Floer homology groups of the closed 3-manifold in our main example and thus can be used as a starting point for an adiabatic limit argument.

math.SG↗

Lagrangian boundary conditions for anti-self-dual instantons and the Atiyah-Floer conjecture

The purpose of this survey is to explain an approach to the Atiyah-Floer conjecture via a new instanton Floer homology with Lagrangian boundary conditions. This is a joint project with Dietmar Salamon. This paper also provides a rough guide to the analysis of anti-self-dual instantons with Lagrangian boundary conditions (in earlier papers), which is the crucial ingredient of our approach.

math.SG↗

Energy identity for anti-self-dual instantons on C\timesΣ

We prove an energy identity for anti-self-dual connections on the product C\timesΣof the complex plane and a Riemann surface. The energy is a multiple of a basic constant that is determined from the values of a corresponding Chern-Simons functional on flat connections and its ambiguity under gauge transformations. For SU(2)-bundles this identity supports the conjecture that the finite energy anti-self-dual instantons correspond to holomorphic bundles over CP^1\timesΣ. Such anti-self-dual instantons on SU(n)- and SO(3)-bundles arise in particular as bubbles in adiabatic limits occurring in the context of mirror symmetry and the Atiyah-Floer conjecture. Our identity proves a quantization of the energy of these bubbles that simplifies and strengthens the involved analysis.

math.DG↗

Energy quantization and mean value inequalities for nonlinear boundary value problems

We give a unified statement and proof of a class of wellknown mean value inequalities for nonnegative functions with a nonlinear bound on the Laplacian. We generalize these to domains with boundary, requiring a (possibly nonlinear) bound on the normal derivative at the boundary. These inequalities give rise to an energy quantization principle for sequences of solutions of boundary value problems that have bounded energy and whose energy densities satisfy nonlinear bounds on the Laplacian and normal derivative: One obtains local uniform bounds on the complement of finitely many points, where some minimum quantum of energy concentrates.

math.AP↗

Anti-self-dual instantons with Lagrangian boundary conditions II: Bubbling

We study bubbling phenomena of anti-self-dual instantons on $\H^2\times§$, where $§$ is a closed Riemann surface. The restriction of the instanton to each boundary slice $\{z\}\times§$, $z\in\pd\H^2$ is required to lie in a Lagrangian submanifold of the moduli space of flat connections over $§$ that arises from the restrictions to the boundary of flat connections on a handle body. We establish an energy quantization result for sequences of instantons with bounded energy near $\{0\}\times§$: Either their curvature is in fact uniformly bounded in a neighbourhood of that slice (leading to a compactness result) or there is a concentration of some minimum quantum of energy. We moreover obtain a removable singularity result for instantons with finite energy in a punctured neighbourhood of $\{0\}\times§$. This completes the analytic foundations for the construction of an instanton Floer homology for 3-manifolds with boundary. This Floer homology is an intermediate object in the program proposed by Salamon for the proof of the Atiyah-Floer conjecture for homology-3-spheres. In the interior case, for anti-self-instantons on $\R^2\times§$, our methods provide a new approach to the removable singularity theorem by Sibner-Sibner for codimension 2 singularities with a holonomy condition.

math.SG↗

Anti-self-dual instantons with Lagrangian boundary conditions I : Elliptic theory

We study a nonlocal boundary value problem for anti-self-dual instantons on 4-manifolds with a space-time splitting of the boundary. The model case is $\R \times Y$, where $Y$ is a compact oriented 3-manifold with boundary $Σ$. The restriction of the instanton to each time slice ${t}\timesΣ$ is required to lie in a fixed (singular) Lagrangian submanifold of the moduli space of flat connections over $Σ$. We establish the basic regularity and compactness properties (assuming $L^p$-bounds on the curvature) as well as the Fredholm theory in a compact model case. The motivation for studying this boundary value problem lies in the construction of instanton Floer homology for 3-manifolds with boundary. The present paper is part of a program proposed by Salamon for the proof of the Atiyah-Floer conjecture for homology-3-spheres.

math.AP↗

Banach space valued Cauchy-Riemann equations with totally real boundary conditions

The main purpose of this paper is to give a general regularity result for Cauchy-Riemann equations in complex Banach spaces with totally real boundary conditions. The usual elliptic $L^p$-regularity results hold true under one crucial assumption: The totally real submanifold has to be modelled on an $L^p$-space or a closed subspace thereof. Secondly, we describe a class of examples of such totally real submanifolds, namely gauge invariant Lagrangian submanifolds in the space of connections over a Riemann surface. These pose natural boundary conditions for the anti-self-duality equation on 4-manifolds with a boundary space-time splitting, leading towards the definition of a Floer homology for 3-manifolds with boundary, which is the first step in a program by Salamon for the proof of the Atiyah-Floer conjecture. The principal part of such a boundary value problem is an example of a Banach space valued Cauchy-Riemann equation with totally real boundary condition.

math.AP↗