Date/Time : 28 Jan 2019 15:00
Venue : S17 #04-06 SR1
Speaker : Zhang Zhiyuan, Institute for Advanced Study

Date/Time:28 Jan 2019 15:00 Venue: S17 #04-06 SR1 Speaker: Zhang Zhiyuan, Institute for Advanced Study Zimmer’s conjecture for simple complex Lie groups We will discuss Zimmer’s conjecture on the actions of lattices in higher rank Lie groups on manifolds of small dimension. This conjecture is recently proved by Aaron Brown, David Fisher and Sebastian Hurtado for real split simple Lie groups. We discuss the proof of this conjecture for simple complex Lie groups. We also give significant improvements for the dimensional bounds for many other non-split Lie groups. This is a joint work with Jinpeng An and Aaron Brown. Add to calendar: 

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Date/Time : 17 Jan 2019 15:00
Venue : S17 #04-05 SR2
Speaker : Lee Ching-pei, University of Wisconsin-Madison

Date/Time:17 Jan 2019 15:00 Venue: S17 #04-05 SR2 Speaker: Lee Ching-pei, University of Wisconsin-Madison Convergence Rates for some Fundamental Algorithms for Continuous Minimization of functions that are a sum of a smooth part and a convex but possibly nonsmooth part that promotes regularization is prevalent in many ap- plication areas, and proximal-type methods are the most eective algorithms for such regularized optimization problems. In this talk, I will present our re- cent advancements on the convergence analysis of rst-order and second-order proximal-type methods for regularized optimization in [1, 2]. I will rst show that the long-known O(1/k) convergence rate on convex problems of gradient descent and coordinate descent in the function value is not tight and can be improved to o(1/k), and extend this result to proximal gradient and proximal coordinate descent for regularized optimization. The second part of this talk will focus on a general framework of inexact successive quadratic approxima- tion that has second-order proximal methods including proximal Newton and proximal quasi-Newton as special cases. Global convergence rates for strongly convex, convex, and nonconvex problems will be discussed. References: [1] Ching-pei Lee and Stephen J. Wright. First-order algorithms converge faster than O(1=k) on convex problems. Technical report, December 2018. URL http://www.optimization-online.org/DB_HTML/2018/12/6993.html. [2] Ching-pei Lee and Stephen J. Wright. Inexact successive quadratic approx- imation for regularized optimization. Computational Optimization and Ap- plications, 2019+. URL http://www.optimization-online.org/DB_HTML/ 2018/03/6499.html. Accepted. Add to calendar: 

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Date/Time : 15 Jan 2019 15:00
Venue : S17 #04-05 SR2
Speaker : Leonard Huang , University of Nevada, Reno, USA

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Date/Time : 30 Nov 2018 15:00
Venue : S17 #04-06 SR1
Speaker : Yuval Peres, Microsoft Research

Date/Time:30 Nov 2018 15:00 Venue: S17 #04-06 SR1 Speaker: Yuval Peres, Microsoft Research Search games and Kakeya sets I’ll describe a search game with a surprising geometric connection. A hunter and a rabbit move on an n-vertex graph without seeing each other until they meet. At each step, the hunter moves to a neighboring vertex or stays in place, while the rabbit is free to jump to any node. Thus they are engaged in a zero sum game, where the payoff is the capture time. We show that an optimal rabbit strategy for the cycle yields a Kakeya set: a plane set of zero area that contains a unit segment in every direction. Kakeya sets have been studied intensively in harmonic analysis since their discovery by Besicovitch (1919); their connection to search games is new and yields insights in both directions. (Based on joint work with Y. Babichenko, R. Peretz, P. Sousi and P. Winkler, and on earlier work by Adler et al (2003).) Add to calendar: 

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Date/Time : 16 Aug 2018 14:00
Venue : S17 #04-05 SR2
Speaker : Dong Chaoping, Shanghai Normal University

Date/Time:16 Aug 2019 14:00 Venue: S17 #04-05 SR2 Speaker: Dong Chaoping, Shanghai Normal University Dirac cohomology: Towards the classification We will recall necessary math ingredients related to the notion of Dirac cohomology, such as Parthasarathy’s Dirac operator inequality, PRV-component, spin module, the unitarily small convex hull, and the spin norm. Then we will discuss some recent progress towards the classification of irreducible unitary representations with non-vanishing Dirac cohomology. In particular, we will mention a few questions. Add to calendar: 

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