Higgs BUNDLES & HARMONIC MAPS WORKSHOP
January 3-11, 2015
Asheville, NC
We will emphasize and study the role of equivariant harmonic maps as a crucial link between Higgs bundles, geometric structures and representation varieties. After preliminary talks on harmonic maps, Higgs bundles and the geometry of symmetric spaces, further topics will include: Corlette's theorem on the existence of equivariant harmonic maps, relationships between harmonic maps and integrable systems, and harmonic maps to singular spaces. Subsequent talks will be based on current developments in the theory of harmonic maps, Higgs bundles and geometric structures. In particular, applications to studying minimal surfaces in symmetric spaces, deformation spaces of OPERS, the geometry of Anosov representations with quasi-Fuchsian representations and Hitchin representations serving as illustrative examples, and asymptotic analysis of such deformation spaces. The overarching theme may be summarized as follows: how does one unpack the data of Higgs bundles, and via a careful study of harmonic maps, start to understand the geometry of surface group representations in a more explicit way.
Scientific Program
The workshop will consist of whiteboard talks by the participants on the following topics.
Rob Maschal: Higgs bundles background
An outline of the nonabelian Hodge correspondence with focus on Higgs bundles, especially the Hitchin component and $SL(2,\mathbb{C})$.
Suggested literature
- Hitchin's paper: Self duality equations on Riemann surfaces
- Hitchin's paper: Lie groups and Teichmüller space
- Lectures by Steve Bradlow at GEAR junior retreat 2012
- Three Videos: Introduction to Higgs bundles on Reimann surfaces
- Bradlow-lecture1-slides.pdf
- Bradlow-lecture2-slides.pdf
- Bradlow-lecture3-slides.pdf
- Bradlow-HiggsExercises.pdf
- Bradlow-sample-solutions.pdf
- Bradlow-HiggsResources.pdf
- Lectures by Peter Gothen at Isaac Newton Institure for Mathematical Sciences
Tengren Zhang: Geometry of symmetric and homogeneous spaces
Semisimple Lie groups: Cartan decompositions, Riemannian geometry, and boundaries of the associated symmetric spaces.
Suggested literature
- Helgason's book: Differential geometry, Lie groups and symmetric spaces
- Chapter 1 of Burstall et al's book: Twistor theory for Riemannian Symmetric spaces
Jérémy Toulisse: Existence theory for harmonic metrics
Corlette's teorem
Suggested literature
- Eels and Sampson paper: Harmonic mappings of Riemannian manifolds
- Simon Donaldson: Twisted harmonic maps and the self-duality equations
- Kevin Corlette: Canonical metrics on flat G-bundles
- François Labourie: Existence D'Applications Harmoniques Tordues à Valeurs Dans les Variétés à Courbure Négative
Semin Kim: Harmonic maps to $\mathbb{R}$-trees and Morgan Shalen compactification
Suggested literature
- Mike Wolf's paper: On Realizing measured foliations via quadratic differentials of harmonic maps to R-trees
- Daskalopoulos, Dostoglu, and Wentworth paper: Character variety and harmonic maps to R-tree
Andrew Sanders: Background on Labourie's conjecture on existence and uniqueness of minimal surfaces for Hitchin representations
Suggested literature
- François Labourie's paper: Cross ratios, Anosov representations and the energy functional on Teichmuller space
- David Baraglia's Thesis: G2 Geometries and integrable systems
Marco Spinaci: Labourie's recent paper: Cyclic surfaces and Hitchin components in rank 2
Suggested literature
- François Labourie's paper: Cyclic surfaces and Hitchin components in rank 2
Qiongling Li: Background on harmonic maps to metric spaces and survey of Katzarkov, Noll, Pandit, and Simpson's paper: Harmonic maps to Buildings and Singular perturbation theory
Suggested literature
- Gromov and Schoen's paper: Harmonic maps into singular spaces and p-adic superrigidity for lattices in groups of rank one
- Korevaar and Schoen's paper: Sobolev spaces and harmonic maps for metric space targets
- Katzarkov, Noll, Pandit, and Simpson's paper: Harmonic maps to Buildings and Singular perturbation theory
Jorge Acosta: OPERS and complex projective structures
Suggested literature
- Dalakov's Thesis: Higgs bundles and Opers
- Dumas's survey: Complex projective structures
- Wentworth's notes: Higgs bundles and local systems on Riemann surfaces
Brian Collier: The relationship between Integrable systems and Harmonic maps with emphasis on the Toda lattice
Suggested literature
- Martin Guest's book: Harmonic Maps, Loop Groups, and Integrable systems
- Aspects of mathematics book: Harmonic Maps and Integrable systems (selected chapters)
- Bolton, Pedit and Woodwards paper: Minimal surfaces and the affine Toda model
Andy Huang: The relationship between integrable systems and harmonic maps with emphasis on the Toda lattice
Suggested literature
- Martin Guest's book: Harmonic Maps, Loop Groups, and Integrable systems
- Aspects of mathematics book: Harmonic Maps and Integrable systems (selected chapters)
- Bolton, Pedit and Woodwards paper: Minimal surfaces and the affine Toda model
Brice Loustau: Minimal surfaces in $\mathbb{H}^3$ and quasi-Fuchsian representations
Minimal surfaces as equivariant harmonic maps, Taubes moduli space of minimal hyperbolic germs, explicit examples of corresponding $SL(2,\mathbb{C})$ Higgs bundles.
Suggested literature
- Taubes paper: Moduli space of minimal hyperbolic germs
- Donaldson's paper: Moment maps in differential geometry
- Thomas Hodge's paper: Hyper-Kahler geometry and Teichmüler space
Jakob Blaavand: Exposition of “Ends of the Moduli Space of Higgs Bundles” by Mazzeo, Swoboda, Weiss, Witt
Suggested literature
- Mazzeo, Swoboda, Weiss, Witt's paper: Ends of the moduli space of Higgs bundles
Laura Fredrickson: Survey of Taubes’s paper $PSL(2,\mathbb{C})$-connections with $L^2$ bounds on curvature
Suggested literature
- Taubes’s paper: $PSL(2,\mathbb{C})$-connections with $L^2$ bounds on curvature
Daniele Alessandrini: Branched hyperbolic surfaces and nonmaximal $SL(2,\mathbb{R})$ representations/Higgs bundles
Suggested literature
- Hitchin's paper: The self-duality equations on a Riemann surface
- Goldman's paper: Higgs bundles and geometric structures on surfaces
Participants
- Jorge Acosta
- Daniele Alessandrini
- Jakob Blaavand
- Brian Collier
- Laura Fredrickson
- Andy Huang
- Semin Kim
- Georgios Kydonakis
- Qiongling Li
- Brice Loustau
- Robert Maschal
- Andrew Sanders
- Marco Spinaci
- Bo Tian
- Jérémy Toulisse
- Tengren Zhang