Colloquia & Seminars Archives - Page 143 of 153

Seminars: Colloquia & Seminars

Date
Time
Venue

Speaker
Affiliation
Title of Talk

12 Sep 2019
17:00
S17 #06-11

Gao Ziyuan
National University of Singapore
The one-cop-moves game on planar graphs

The one-cop-moves game on planar graphs

Date/Time : 12 Sep 2019 17:00
Venue : S17 #06-11
Speaker : Gao Ziyuan, National University of Singapore

Date/Time:12 Sep 2019 17:00 Venue: S17 #06-11 Speaker: Gao Ziyuan, National University of Singapore The one-cop-moves game on planar graphs Cops and Robbers is a vertex-pursuit game played on graphs. In this game, a set of cops and a robber occupy the vertices of the graph and move alternately along the graph’s edges with perfect information about each other’ positions. If a cop eventually occupies the same vertex as the robber, then the cops win; the robber wins if she can indefinitely evade capture. Aigner and Fromme established that in every connected planar graph, three cops are sufficient to capture a single robber. In this paper, we consider a recently studied variant of the cops and robbers game, alternately called the one-active-cop game, one-cop-moves game or the lazy cops and robbers game, where at most one cop can move during any round. We show that Aigner and Fromme’s result does not generalize to this game variant by constructing a connected planar graph on which a robber can indefinitely evade three cops in the one-cop-moves game. This talk is based on joint work with Boting Yang (http://www2.cs.uregina.ca/~boting/). Add to calendar:

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11 Sep 2019
16:00
S17 #05-11 SR5

Krishna Balasubramanian
UC Davis
Applications of Gaussian Stein’s Identity to Non-Convex Optimization and Sampling

Applications of Gaussian Stein’s Identity to Non-Convex Optimization and Sampling

Date/Time : 11 Sep 2019 16:00
Venue : S17 #05-11 SR5
Speaker : Krishna Balasubramanian, UC Davis

Date/Time:11 Sep 2019 16:00 Venue: S17 #05-11 SR5 Speaker: Krishna Balasubramanian, UC Davis Applications of Gaussian Stein’s Identity to Non-Convex Optimization and Sampling Optimization and sampling are arguably the computational backbones of Frequentist and Bayesian statistics respectively. In this talk the use of Gaussian Stein’s identity for performing stochastic Zeroth-Order (ZO) non-convex optimization and sampling will be discussed. Specifically, we consider the case when the function (or density) under consideration is not available to us analytically, rather we are able to only obtain noisy evaluations. Using Gaussian Stein’s identity, techniques for estimating the gradient and Hessian of a function (or density) will be introduced. Based on this, the following algorithms and the corresponding theoretical results will be discussed: (i) ZO stochastic gradient method in high-dimensions (ii) ZO Newton’s method for escaping saddle points (iii) ZO Euler and Ozaki discretized (Kinetic) Langevin Monte Carlo sampling. Add to calendar:

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11 Sep 2019
16:00
S17 #04-04 SR3

Arielle Leitner
Weizmann Institute
Generalized Cusps on Convex Projective Manifolds

Generalized Cusps on Convex Projective Manifolds

Date/Time : 11 Sep 2019 16:00
Venue : S17 #04-04 SR3
Speaker : Arielle Leitner , Weizmann Institute

Date/Time:11 Sep 2019 16:00 Venue: S17 #04-04 SR3 Speaker: Arielle Leitner , Weizmann Institute Generalized Cusps on Convex Projective Manifolds Convex projective manifolds are a generalization of hyperbolic manifolds. Koszul showed that the set of holonomies of convex projective structures on a compact manifold is open in the representation variety. We will describe an extension of this result to convex projective manifolds whose ends are generalized cusps, due to Cooper-Long-Tillmann. Generalized cusps are certain ends of convex projective manifolds. They may contain both hyperbolic and parabolic elements. We will describe their classification (due to Ballas-Cooper-Leitner), and explain how generalized cusps turn out to be deformations of cusps of hyperbolic manifolds. If time permits we will discuss current work on the moduli space of generalized cusps (joint with Ballas and Cooper). Add to calendar:

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11 Sep 2019
10:00
S16 #03-09

Bao Huanchen
National University of Singapore
Total positivity in reductive groups

Total positivity in reductive groups

Date/Time : 11 Sep 2019 10:00
Venue : S16 #03-09
Speaker : Bao Huanchen, National University of Singapore

Date/Time:11 Sep 2019 10:00 Venue: S16 #03-09 Speaker: Bao Huanchen, National University of Singapore Total positivity in reductive groups I will explain Lusztig’s theory of total positivity. I shall follow (mainly) his 1994 paper of the same title. Add to calendar:

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05 Sep 2019
17:00
S17 #06-11

Samuel Alfaro Tanuwijaya

Pseudo-finite fields

Pseudo-finite fields

Date/Time : 05 Sep 2019 17:00
Venue : S17 #06-11
Speaker : Samuel Alfaro Tanuwijaya,

Date/Time:05 Sep 2019 17:00 Venue: S17 #06-11 Speaker: Samuel Alfaro Tanuwijaya Pseudo-finite fields This talk will introduce pseudofinite fields and how they are axiomatized. We will see how they are infinite models of the theory of finite fields, and therefore there is no theory whose models are exactly the finite fields. Add to calendar:

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04 Sep 2019
16:00
S17 #05-11 SR5

Marko Hans Weber
National University of Singapore
Models with Price Impact

Models with Price Impact

Date/Time : 04 Sep 2019 16:00
Venue : S17 #05-11 SR5
Speaker : Marko Hans Weber, National University of Singapore

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04 Sep 2019

90th Anniversary Distinguished Lecture

Date/Time : 04 Sep 2019
Venue :
Speaker : ,

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04 Sep 2019
10:00
S16 #03-09

Cheng Yao
Sinica
Special Value formula for twisted triple product L-function and an application to the restricted L^2-norm problem

Special Value formula for twisted triple product L-function and an application to the restricted L^2-norm problem

Date/Time : 04 Sep 2019 10:00
Venue : S16 #03-09
Speaker : Cheng Yao, Sinica

Date/Time:04 Sep 2019 10:00 Venue: S16 #03-09 Speaker: Cheng Yao, Sinica Special Value formula for twisted triple product L-function and an application to the restricted L^2-norm problem In this talk we will present an explicit Ichino’s formula [Ich08] for the central value of the twisted triple product L-function associated to Maass forms. To establish such a formula one need to carry out explicit computations for the local period integrals appearing in Ichino’s formula. We prove an identity between the local period integral and a product of two Rankin-Selberg integrals in order to simplify the calculations. This identity generalizes the result in [MV10]. Our explicit formula has an application to the optimal upper bound of a sum of restricted L^2-norms of the L^2-normalized newforms on certain quadratic extensions with prime level and bounded spectral parameter. For this we follow the methods in [Blo13]. References: [Blo13] Valentin Blomer. On the 4-norm of an automorphic form. Journal of European Mathematical Society, 15:1825–1852, 2013. [Ich08] A. Ichino. Trilinear forms and the central values of triple product L-functions. Duke Mathematical Journal, 145(2):281– 307, 2008. [MV10] P. Michel and A. Venkatesh. The subconvexity problem for GL2. Publ. Math. Inst. Hautes Etudes Sci., (111):171–271, 2010. Add to calendar:

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29 Aug 2019
17:00
S17 #06-11

Chong Chi Tat
National University of Singapore
Revisiting Seetapun’s theorem with his disjunction

Revisiting Seetapun’s theorem with his disjunction

Date/Time : 29 Aug 2019 17:00
Venue : S17 #06-11
Speaker : Chong Chi Tat, National University of Singapore

Date/Time:29 Aug 2019 17:00 Venue: S17 #06-11 Speaker: Chong Chi Tat, National University of Singapore Revisiting Seetapun’s theorem with his disjunction Ramsey’s theorem RT^n_2 states that if the n-rtuples of the set of natural numbers are coloured in either red or blue, then there is an infinite subset all of whose n-tuples have the same color. The proof-theoretic strength of RT^n_2 has been a prominent line of study in reverse mathematics. The first major breakthrough was obtained by David Seetapun (Seetapun and Slaman (1995)) who showed that RT^2_2 is strictly weaker than RT^3_2. This talk will describe a proof of this theorem using the technique called “Seetapun disjunction” introduced in Chong, Slaman and Yang (2014). Add to calendar:

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