Conference Schedule for 29th Annual Geometry Festival

# 29th Annual Geometry Festival

## Conference Schedule

 Friday, April 11 4:00pm Robert Bryant, Duke University Rolling surfaces and exceptional geometry The mechanical system of one rigid surface rolling over another without twisting or slipping is a staple of non-holonomic mechanics and has been studied from a number of different points of view. The differential equations that describe this motion turn out to be a special case of a system of PDE studied by Élie Cartan in 1910. Remarkably, Cartan showed that such systems can have a symmetry group with dimension as large as 14 (and that, in this case, the symmetry group is isomorphic to the exceptional group $G_2$). For example, it turns out that a sphere of radius~$1$ rolling over a sphere of radius~$3$ belongs to this highly symmetric case. In recent years, interest in these systems have come from a number of different sources, and there have been some surprising developments. P. Nurowski has shown that there is a close connection of Cartan's work with split-conformal geometry in dimension~$5$, and T. Willse has shown that there is a connection with pseudo-Riemannian metrics of special holonomy in dimension~$7$. Quite recently, Nurowski and An have used this connection to discover a remarkable convex surface in $3$-space whose differential constraints that describe its rolling over the flat plane have $G_2$-symmetry, which raises the question of how many such pairs of surfaces might exist. In this talk, I will describe the history of this problem, the geometry that goes into its study, and the above recent developments in this area, including some recent results of my own that provide progress in classifying the pairs of surfaces whose rolling constraints have exceptional symmetry. Saturday, April 12 9:15am Jim Simons, Stony Brook University Opening Remarks 9:30am Robert Haslhofer, New York University Mean curvature flow with surgery We give a new proof for the existence of mean curvature flow with surgery for 2-convex hypersurfaces. Our proof works in all dimensions, including mean convex surfaces in $R^3$. We also derive a priori estimates for a more general class of flows. This is joint work with Bruce Kleiner. 11:00am André Neves, Imperial College Existence of minimal hypersurfaces I will talk about my recent work with Fernando Marques where we show that positive ricci curvature metrics admit an infinite number of minimal embedded hypersurfaces. 1:30pm Song Sun, SCGP and Stony Brook University Kahler-Einstein metrics: Gromov-Hausdorff limits and algebraic geometry In this talk we will discuss compactification of the moduli space of Kahler-Einstein manifolds using Gromov-Hausdorff limits, in both abstract and explicit terms, and emphasize the relation with algebraic geometry. This is based on joint works with Donaldson, Chen-Donaldson, and Odaka-Spotti. 3:00pm Matthew Gursky, Notre Dame University Critical metrics on connected sums of Einstein four-manifolds I will describe joint work with J. Viaclovsky in which we use a gluing construction to produce new examples of four-manifolds that are critical for certain quadratic Riemannian curvature functionals. The main application is an existence result, using two well-known Einstein manifolds as building blocks: the Fubini-Study metric on $CP^2$, and the product metric on $S^2 x S^2$. Using these metrics in various gluing configurations, critical metrics are found on connected sums. 5:00pm Alice Chang, Princeton University On positivity of a class of conformal covariant operators I will report on a recent joint work with Jeffrey Case in which we study the positivity of a class of non-local conformal covariant operators which are fractional GJMS operators defined via scattering theory on asymptotic hyperbolic manifolds, which includes the Dirichlet-Neumann operator as a special case. When the order of the operator is higher than 2, we will explore the positivity property of this class of operators via Sobolov trace extension formulas in the setting of metric spaces with measures. Sunday, April 13 9:30am Kenji Fukaya, SCGP and Stony Brook University 'Hodge Theory' from Floer homology In this talk I want to report some resent progress of the project in the title.  In our previous work with Oh, Ohta, Ono, we established relation between Jacobian ring of super potential defined by Lagrangian Floer theory on Toric manifolds and Quantum cohomology.  We also establish certain pairing in Jacobian ring and Hochshild homology (jointly also with Abouzaid) and relate it to the Poincare pairing in Quantum cohomology.  We are now studying, higher residue pairing and primitive form (of Kyoji Saitoh) in the LG model of super potential which is Hodge theoretical part of LG model, and its relation to cyclic homology and also to $S^1$ equivariant Gromov-Witten theory.  (Many parts of this story are work in progress.) 11:00am Herman Gluck, University of Pennsylvania History of the Geometry Festival 11:10am Mihalis Dafermos, Princeton University On null singularities for the Einstein vacuum equations and the strong cosmic censorship conjecture in general relativity I will present new results on the emergence of "null singularities" in the interior of generic vacuum black hole spacetimes (without symmetry assumptions), and I will discuss what this means for the status of Penrose's celebrated strong cosmic censorship conjecture in general relativity. This is joint work with Jonathan Luk (MIT).

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