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# Timetable (MOSW01)

## School on Moduli Spaces

Wednesday 5th January 2011 to Friday 14th January 2011

 09:00 to 09:55 Registration 09:55 to 10:00 Welcome from Sir David Wallace (INI Director) 10:00 to 11:00 N Hoffmann (Freie Universität Berlin)Augmented bundles - I The notion of augmented bundle comprises various extra structures on vector bundles. The lectures deal with examples like quasiparabolic bundles, coherent systems, framed bundles, Higgs bundles, and holomorphic triples, all on a compact Riemann surface. I'll explain their coarse moduli spaces and discuss the role of the stability parameters. INI 1 11:00 to 11:30 Morning coffee 11:30 to 12:30 T Gómez (Universidad Complutense de Madrid)Principal bundles - I This is an introduction to principal bundles in algebraic geometry. We will start with the basic definitions (associated fibrations, reduction and extension of structure group, stability, etc...) and then give a sketch of the construction of the moduli Notes: The following are the notes of some lectures I gave in Warsaw. In that school I gave 5 lectures, so this time I won't be able to cover all this material, but this could serve as a reference: T. Gomez, Lectures on principal bundles over projective varieties, Pragacz, P. (Ed.) Algebraic cycles, sheaves, shtukas, and moduli. Impanga lecture notes. Trends in Mathematics. Birkh\"auser Verlag, Basel, 2008. viii+236 pp., 45--68. Lectures on Principal Bundles over proyective varieties. arXiv: 1011.1801v1 INI 1 12:30 to 13:30 Lunch at Wolfson Court 14:00 to 15:00 B Doran (ETH Zürich)Geometric Invariant Theory - I INI 1 15:00 to 15:30 Afternoon tea 15:30 to 16:30 N Nitsure (Tata Institute of Fundamental Research)Deformation Theory : an introduction to the algebraic approach - I This series of three lectures aims to give an introduction to the algebraic approach to deformation theory, as developed by Grothendieck, Schlessinger, Illusie and Artin, illustrated with a few key examples. The topics will include (i) infinitesimal theory over Artin local rings including Schlessinger's theorem, tangent-obstruction theories and use of cotangent complex, (ii) algebraization via the Grothendieck existence theorem for formal schemes and the Artin approximation theorem, and (iii) construction of global moduli as quotient algebraic spaces. INI 1 16:45 to 17:45 Tutorials INI 1 17:45 to 18:45 Welcome wine reception 18:45 to 19:30 Dinner at Wolfson Court (residents only)
 10:00 to 11:00 N Hoffmann (Freie Universität Berlin)Augmented bundles - II The notion of augmented bundle comprises various extra structures on vector bundles. The lectures deal with examples like quasiparabolic bundles, coherent systems, framed bundles, Higgs bundles, and holomorphic triples, all on a compact Riemann surface. I'll explain their coarse moduli spaces and discuss the role of the stability parameters. INI 1 11:00 to 11:30 Morning coffee 11:30 to 12:30 T Gómez (Universidad Complutense de Madrid)Principal bundles - II This is an introduction to principal bundles in algebraic geometry. We will start with the basic definitions (associated fibrations, reduction and extension of structure group, stability, etc...) and then give a sketch of the construction of the moduli Notes: The following are the notes of some lectures I gave in Warsaw. In that school I gave 5 lectures, so this time I won't be able to cover all this material, but this could serve as a reference: T. Gomez, Lectures on principal bundles over projective varieties, Pragacz, P. (Ed.) Algebraic cycles, sheaves, shtukas, and moduli. Impanga lecture notes. Trends in Mathematics. Birkh\"auser Verlag, Basel, 2008. viii+236 pp., 45--68. Lectures on Principal Bundles over proyective varieties. arXiv: 1011.1801v1 INI 1 12:30 to 13:30 Lunch at Wolfson Court 14:00 to 15:00 B Doran (ETH Zürich)Geometric Invariant Theory - II INI 1 15:00 to 15:30 Afternoon tea 15:30 to 16:30 N Nitsure (Tata Institute of Fundamental Research)Deformation Theory : an introduction to the algebraic approach - II This series of three lectures aims to give an introduction to the algebraic approach to deformation theory, as developed by Grothendieck, Schlessinger, Illusie and Artin, illustrated with a few key examples. The topics will include (i) infinitesimal theory over Artin local rings including Schlessinger's theorem, tangent-obstruction theories and use of cotangent complex, (ii) algebraization via the Grothendieck existence theorem for formal schemes and the Artin approximation theorem, and (iii) construction of global moduli as quotient algebraic spaces. INI 1 16:45 to 17:45 Tutorials INI 1 18:45 to 19:30 Dinner at Wolfson Court (residents only)
 10:00 to 11:00 P Gothen (Universidade do Porto)Representations of surface groups and Higgs bundles - I Classical Hodge theory uses harmonic forms as preferred representatives of cohomology classes. A representation of the fundamental group of a Riemann surface gives rise to a corresponding flat bundle. A Theorem of Donaldson and Corlette shows how to find a harmonic metric in this bundle. A flat bundle corresponds to class in first non-abelian cohomology and the Theorem can be viewed as an analogue of the classical representation of de Rham cohomology classes by harmonic forms. INI 1 11:00 to 11:30 Morning coffee 11:30 to 12:30 E Diaconescu ([Rutgers])Moduli spaces and physics INI 1 12:30 to 13:30 Lunch at Wolfson Court 14:00 to 15:00 B Doran (ETH Zürich)Geometric Invariant Theory - III INI 1 15:00 to 15:30 Afternoon tea 15:30 to 16:30 N Nitsure (Tata Institute of Fundamental Research)Deformation Theory : an introduction to the algebraic approach - III This series of three lectures aims to give an introduction to the algebraic approach to deformation theory, as developed by Grothendieck, Schlessinger, Illusie and Artin, illustrated with a few key examples. The topics will include (i) infinitesimal theory over Artin local rings including Schlessinger's theorem, tangent-obstruction theories and use of cotangent complex, (ii) algebraization via the Grothendieck existence theorem for formal schemes and the Artin approximation theorem, and (iii) construction of global moduli as quotient algebraic spaces. INI 1 16:45 to 17:45 Tutorials INI 1 18:45 to 19:30 Dinner at Wolfson Court (residents only)
 10:00 to 11:00 B Doran (ETH Zürich)Geometric Invariant Theory - IV 11:00 to 11:30 Morning coffee - served at INI 11:30 to 12:30 P Gothen (Universidade do Porto)Representations of surface groups and Higgs bundles - II A Higgs bundle on a Riemann surface is a pair consisting of a holomorphic bundle and a holomorphic one-form, the Higgs field, with values in a certain associated vector bundle. A theorem of Hitchin and Simpson says that a stable Higgs bundle admits a metric satisfying Hitchin's equations. Together with the Theorem of Corlette and Donaldson, the Hitchin-Kobayashi correspondence generalizes the classical Hodge decomposition of the first cohomology of the Riemann surface, providing a correspondence between isomorphism classes of Higgs bundles and representations of the fundamental group of the surface. 12:30 to 13:30 Lunch at Wolfson Court 14:00 to 15:00 D Huybrechts ([Bonn])Introduction to derived categories and stability conditions - I The title may be misleading, I will actually assume the audience to be familiar with the basic concepts of derived and triangulated categories. (I might however recall the notion of t-structures.) The emphasis will be on stability conditions. I plan to introduce stability conditions in the sense of Bridgeland (and Kontsevich-Soibelman) and discuss examples. The relevant literature is accessible on the arxiv. 15:00 to 15:30 Afternoon tea - served at INI 15:30 to 16:30 V Alexeev ([Georgia])Introduction to moduli of varieties - I: Generalities on moduli spaces of varieties The yoga of moduli spaces. Main methods of construction. Compactifications and Minimal Model Program. Stable pairs (slc & ample K+B). Honest work vs "accidental" examples. 16:45 to 17:45 Tutorials INI 1 18:45 to 19:30 Dinner at Wolfson Court (residents only)
 10:00 to 11:00 K Behrend ([British Columbia])Introduction to stacks - I Introduction to algebraic stacks as they are relevant to moduli theory. 11:00 to 11:30 Morning coffee - served at INI 11:30 to 12:30 P Gothen (Universidade do Porto)Representations of surface groups and Higgs bundles - III In the final lecture, we give some applications of Higgs bundle theory to the study of the geometry and topology of character varieties for surface groups, via the identification with moduli of Higgs bundles. 12:30 to 13:30 Lunch at Wolfson Court 14:00 to 15:00 D Huybrechts ([Bonn])Introduction to derived categories and stability conditions - II The title may be misleading, I will actually assume the audience to be familiar with the basic concepts of derived and triangulated categories. (I might however recall the notion of t-structures.) The emphasis will be on stability conditions. I plan to introduce stability conditions in the sense of Bridgeland (and Kontsevich-Soibelman) and discuss examples. The relevant literature is accessible on the arxiv. 15:00 to 15:30 Afternoon tea - served at INI 15:30 to 16:30 V Alexeev ([Georgia])Introduction to moduli of varieties - II: Stable toric and semiabelic varieties Moduli of stable toric varieties vs toric Hilbert scheme. Convex tilings and secondary polytopes. Degenerations of abelian varieties. Semiabelian and semiabelic varieties. Compactifications of moduli spaces of abelian varieties. Refs: http://arxiv.org/abs/math/9905103, http://arxiv.org/abs/math/0207272, http://arxiv.org/abs/math/0207274. 16:45 to 17:45 Tutorials INI 1 18:45 to 19:30 Dinner at Wolfson Court (residents only)
 10:00 to 11:00 K Behrend ([British Columbia])Introduction to stacks - II Introduction to algebraic stacks as they are relevant to moduli theory. 11:00 to 11:30 Morning coffee - served at INI 11:30 to 12:30 M Reineke (Bergische Universität Wuppertal)Ringel-Hall algebras and applications to moduli - I Moduli spaces of representations of quivers, parametrizing configurations of vector spaces and linear maps up to base change, provide a prototype for many moduli spaces of algebraic geometry. The Hall algebra of a quiver, a convolution algebra of functions on stacks of its representations, can be used to obtain quantitative information on the moduli spaces: algebraic identities in the Hall algebra, proved by representation-theoretic techniques, yield identities for e.g. Betti numbers or numbers of points over finite fields. We will develop several such identities and discuss more recent applications to wall-crossing formulae. Notes: Several of the Hall algebra techniques which I would like to discuss are reviewed in the survey "Moduli of representations of quivers", arXiv:0802.2147. Although this paper was written for an audience of representation theorists, it might as well be helpful for the participants of the School on Moduli Spaces. The more recent applications to wall-crossing formulae are developed in "Poisson automorphisms and quiver moduli", arXiv:0802.2147. 12:30 to 13:30 Lunch at Wolfson Court 14:00 to 15:00 D Huybrechts ([Bonn])Introduction to derived categories and stability conditions - III The title may be misleading, I will actually assume the audience to be familiar with the basic concepts of derived and triangulated categories. (I might however recall the notion of t-structures.) The emphasis will be on stability conditions. I plan to introduce stability conditions in the sense of Bridgeland (and Kontsevich-Soibelman) and discuss examples. The relevant literature is accessible on the arxiv. 15:00 to 15:30 Afternoon tea - served at INI 15:30 to 16:30 V Alexeev ([Georgia])Introduction to moduli of varieties - III: Weighted hyperplane arrangements $\bar M_{0,n}$. Hassett's weighted stable curves. Compact moduli of weighted hyperplane arrangements. Refs: http://arxiv.org/abs/math/0205009, http://arxiv.org/abs/math/0501227, http://arxiv.org/abs/0806.0881 16:45 to 17:45 Tutorials INI 1 19:30 to 22:00 Conference dinner at Emmanuel College
 10:00 to 11:00 K Behrend ([British Columbia])Introduction to stacks - III Introduction to algebraic stacks as they are relevant to moduli theory. 11:00 to 11:30 Morning coffee - served at INI 11:30 to 12:30 M Reineke (Bergische Universität Wuppertal)Ringel-Hall algebras and applications to moduli - II Moduli spaces of representations of quivers, parametrizing configurations of vector spaces and linear maps up to base change, provide a prototype for many moduli spaces of algebraic geometry. The Hall algebra of a quiver, a convolution algebra of functions on stacks of its representations, can be used to obtain quantitative information on the moduli spaces: algebraic identities in the Hall algebra, proved by representation-theoretic techniques, yield identities for e.g. Betti numbers or numbers of points over finite fields. We will develop several such identities and discuss more recent applications to wall-crossing formulae. Notes: Several of the Hall algebra techniques which I would like to discuss are reviewed in the survey "Moduli of representations of quivers", arXiv:0802.2147. Although this paper was written for an audience of representation theorists, it might as well be helpful for the participants of the School on Moduli Spaces. The more recent applications to wall-crossing formulae are developed in "Poisson automorphisms and quiver moduli", arXiv:0802.2147. 12:30 to 13:30 Lunch at Wolfson Court 14:00 to 15:00 D Huybrechts ([Bonn])Introduction to derived categories and stability conditions - IV The title may be misleading, I will actually assume the audience to be familiar with the basic concepts of derived and triangulated categories. (I might however recall the notion of t-structures.) The emphasis will be on stability conditions. I plan to introduce stability conditions in the sense of Bridgeland (and Kontsevich-Soibelman) and discuss examples. The relevant literature is accessible on the arxiv. 15:00 to 15:30 Afternoon tea - served at INI 15:30 to 16:30 V Alexeev ([Georgia])Introduction to moduli of varieties - IV: Surfaces of general type related to abelian varieties and hyperplane arrangements Compact moduli of surfaces of general type derived from (1) abelian varieties, (2) line arrangements. Campedelli, Burniat, Kulikov surfaces. Refs: http://arxiv.org/abs/math/9905103, http://arxiv.org/abs/0901.4431 16:45 to 17:45 Tutorials INI 1 18:45 to 19:30 Dinner at Wolfson Court (residents only)
 10:00 to 11:00 K Behrend ([British Columbia])Introduction to stacks - IV Introduction to algebraic stacks as they are relevant to moduli theory. 11:00 to 11:30 Morning coffee - served at INI 11:30 to 12:30 M Reineke (Bergische Universität Wuppertal)Ringel-Hall algebras and applications to moduli - III Moduli spaces of representations of quivers, parametrizing configurations of vector spaces and linear maps up to base change, provide a prototype for many moduli spaces of algebraic geometry. The Hall algebra of a quiver, a convolution algebra of functions on stacks of its representations, can be used to obtain quantitative information on the moduli spaces: algebraic identities in the Hall algebra, proved by representation-theoretic techniques, yield identities for e.g. Betti numbers or numbers of points over finite fields. We will develop several such identities and discuss more recent applications to wall-crossing formulae. Notes: Several of the Hall algebra techniques which I would like to discuss are reviewed in the survey "Moduli of representations of quivers", arXiv:0802.2147. Although this paper was written for an audience of representation theorists, it might as well be helpful for the participants of the School on Moduli Spaces. The more recent applications to wall-crossing formulae are developed in "Poisson automorphisms and quiver moduli", arXiv:0802.2147. 12:30 to 13:30 Lunch at Wolfson Court 14:00 to 15:00 D Huybrechts ([Bonn])Introduction to derived categories and stability conditions - V The title may be misleading, I will actually assume the audience to be familiar with the basic concepts of derived and triangulated categories. (I might however recall the notion of t-structures.) The emphasis will be on stability conditions. I plan to introduce stability conditions in the sense of Bridgeland (and Kontsevich-Soibelman) and discuss examples. The relevant literature is accessible on the arxiv. 15:00 to 15:30 Afternoon tea - served at INI 15:30 to 16:30 V Alexeev ([Georgia])Introduction to moduli of varieties - V: Surfaces of general type: the general case Several versions of the moduli functor. Problems, and some solutions. Steps in the construction of the moduli space. Ref: many older papers, http://arxiv.org/abs/0805.0576, http://arxiv.org/abs/1008.0621 (by Kollár) 16:45 to 17:45 Tutorials INI 1 18:45 to 19:30 Dinner at Wolfson Court (residents only)