The space of (Kahler) metrics on a projective algebraic variety can be given a natural infinite dimensional Riemannian structure. This leads to the notion of a geodesic in the space of metrics. I will discuss a recent result on the optimal regularity of these geodesics and how this relates to nonlinear PDEs and canonical metrics. This is joint work with J. Chu and V. Tosatti.
We briefly describe some ideas and techniques that lead to solutions to certain problems in number theory, such as the bounded gaps between prime numbers, and others. This talk will be made understandable to general math audiences; technical details will be avoided.
We give a new and short proof of spectral localization for the 1-d Anderson model with any disorder. The original proof was given by Carmona-Klein-Martinelli in 1987, based on multi-scale analysis. Our proof is based on the large deviation estimates and positivity and subharmonicity of the Lyapunov exponent. We also show how to improve the estimates to get a uniform and quantitative version that allows us to get the exponential dynamical localization. It is joint work with S. Jitomirskaya. Complete details of the spectral localization proof will be presented during the talk.
The self organization of phospholipids into membranes is fundamental to the origin of life, allowing for protection of internal structure while necessitating machinery to open pores. Evolutionary pressure has designed a myriad of controls in the guise of surface proteins that adjust the entropy of the lipid-solvent interactions, raising and lower energy barriers to membrane fusion, budding, endocytosis, and inducing curvature vectors that encode for fenestration and helical structures. All of these actors orchestrate the delicate dynamics of the endoplasmic reticulum (ER) and associated Golgi apparatus, biology's original coherent structures.
We embed the ER and its dynamics within an energy minimization problem whose coherent dynamics play out on a huge center-stable stage. We given an overview of the bifurcation structure, including a mechanism for the onset of morphological complexity observed in synthetic amphiphilic polymers, and describe the template ER problem: the evolution and budding of lipid droplets.
We will start from the motivation of the tropical geometry. Then
we will explain how to use Lagrangian Floer theory to establish the
correspondence between the weighted counting of tropical curves to the
counting of holomorphic discs in K3 surfaces. In particular, the result
provides the existence of new holomorphic discs which do not come easily
from direct gluing argument.
We will start from the motivation of the tropical geometry. Then
we will explain how to use Lagrangian Floer theory to establish the
correspondence between the weighted counting of tropical curves to the
counting of holomorphic discs in K3 surfaces. In particular, the result
provides the existence of new holomorphic discs which do not come easily
from direct gluing argument.
In this workshop we will discuss techniques to facilitate group work, and make discussion sessions more active. We will also introduce tasks aimed at actively involve students in various phases of the learning process (e.g., introduce/explore/review a topic, learn the steps to solve a particular problem or the lay out of a proof).
Gaussian comparison inequalities are classical tools that often lead to simple proofs of powerful results in random matrix theory, convex geometry, etc. Perhaps the most celebrated of these tools is Slepian’s Inequality, which dates back to 1962. The Gaussian Min-max Theorem (GMT) is a non-trivial generalization of Slepian’s result, derived by Gordon in 1988. Here, we prove a tight version of the GMT in the presence of convexity. Based on that, we describe a novel and general framework to precisely evaluate the performance of non-smooth convex optimization methods under certain measurement ensembles (Gaussian, Haar). We discuss applications of the theory to box-relaxation decoders in massive MIMO, 1-bit compressed sensing, and phase-retrieval.
We describe a number of related questions at the interface of set theory and homology theory, centering on (1) the additivity of strong homology, and (2) the cohomology of the ordinals. In the first, the question is, at heart: To how general a category of topological spaces may classical homology theory be continuously extended? And in the tension between various potential senses of continuity lie a number of delicate set-theoretic questions. These questions led to the consideration of the Cech cohomology of the ordinals; the surprise was that this is a meaningful thing to consider at all. It very much is, describing or suggesting at once (i) distinctive combinatorial principles associated to the nth infinite cardinal, for each n, holding in ZFC, (ii) rich connections between cofinality and dimension, and (iii) higher-dimensional extensions of the method of minimal walks.