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 Events
Aaron Berk
Mathematics, UBC
Fri 20 Oct 2017, 12:00pm
Graduate Student Seminar
MATH 203
From Hoeffding's inequality to PAC learning
MATH 203
Fri 20 Oct 2017, 12:00pm-1:00pm

Abstract

The efficacy of machine learning algorithms hinges on their ability to generalize from data (i.e., when does small training error guarantee small test error). However, the theory of generalizability remains largely unexplained, particularly for monstrous networks that achieve ground-breaking performance on complex tasks like image classification, language translation, or the game Go. The goal of this talk is to showcase how a simple yet elegant phenomenon in probability - concentration of measure - informs the formalization of "learning from data". By way of Hoeffding's inequality, we show how PAC learning uses concentration of measure to address the problem of generalizability in machine learning.

This talk will be accessible to all graduate students and post-docs who've heard the phrase "Markov inequality" at least once. I chose the subject matter because it contains elegant math that yields deep results in an equally elegant formalization of a high-level salient concept. This talk is related but tangential to the subject matter of the probability reading group this term (i.e., I'd be excited to discuss how these results might generalize to more exciting cases).
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Cambridge
Fri 20 Oct 2017, 3:00pm
Department Colloquium
ESB 2012
Universality for the dimer model
ESB 2012
Fri 20 Oct 2017, 3:00pm-4:00pm

Abstract

The dimer model on a finite bipartite graph is a uniformly chosen perfect matching, i.e., a set of edges which cover every vertex exactly once. It is a classical model of mathematical physics, going back to work of Kasteleyn and Temeperley/Fisher in the 1960s, with connections to many topics including determinantal processes, random matrix theory, algebraic combinatorics, discrete complex analysis, etc.

A central object for the dimer model is a notion of height function introduced by Thurston, which turns the dimer model into a random discrete surface. I will discuss a series of recent results with Benoit Laslier (Paris) and Gourab Ray (Victoria) where we establish the convergence of the height function to a scaling limit in a variety of situations. This includes simply connected domains of the plane with arbitrary linear boundary conditions for the height, in which case the limit is the Gaussian free field, and Temperleyan graphs drawn on Riemann surfaces. In all these cases the scaling limit is universal (i.e., independent of the details of the graph) and conformally invariant.

A key new idea in our approach is to exploit "imaginary geometry" couplings between the Gaussian free field and Schramm's celebrated SLE curves.

Note for Attendees

Light refreshments will be served at 2:45pm in ESB 4133, the PIMS Lounge before this colloquium.
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SNS Pisa
Mon 23 Oct 2017, 4:00pm
Algebraic Geometry Seminar
MATH 126
TBA
MATH 126
Mon 23 Oct 2017, 4:00pm-5:00pm

Abstract

 
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McGill
Tue 24 Oct 2017, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
An isometric embedding problem and related geometric inequalities
ESB 2012
Tue 24 Oct 2017, 3:30pm-4:30pm

Abstract

Solutions to the classical Weyl problem by Nirenberg and Pogorelov
play fundamental role in the notion of quasi local masses and positive quasi
local mass theorems in general relativity. An interesting question in
differential geometry is whether one can isometrically embed compact surfaces
with positive Gauss curvature to a general 3 dimensional ambient space. Of
particular importance is the anti de Sitter Schwarzchild space in general
relativity.  We discuss some recent progress in this direction, the a priori
estimates for embedded surfaces in a joint work with Lu, the openness and
non-rigidity results of Li -Wang, and a new quasi local type inequality of
Lu-Miao. We will also discuss open problem related to isometric embeddings to
ambient spaces with horizons.
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UBC
Tue 24 Oct 2017, 4:00pm
Discrete Math Seminar
ESB 4127
Disjoint Cycles and Equitable Colorings in Graphs
ESB 4127
Tue 24 Oct 2017, 4:00pm-5:00pm

Abstract

 
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Jim Bryan
UBC
Mon 30 Oct 2017, 4:00pm
Algebraic Geometry Seminar
MATH 126
TBA
MATH 126
Mon 30 Oct 2017, 4:00pm-5:00pm

Abstract

 
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University of Alberta at Edmonton
Wed 1 Nov 2017, 3:00pm
Probability Seminar
ESB 2012
Feynman-Kac formula for the stochastic heat equation driven by general Gaussian noises
ESB 2012
Wed 1 Nov 2017, 3:00pm-4:00pm

Abstract


In this talk  I will  present some results on stochastic heat equations driven by a Gaussian noises. I will focus on Feynman-Kac representation of the solution and the moments of the solution. Both lower and upper bounds for the L^p moments of the solution are obtained which is relevant to the so-called intermittency. The Driving Gaussian noises include fractional Brownian fields of Hurst parameters greater or smaller than 1/2.
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UBC Math
Fri 3 Nov 2017, 3:00pm
Department Colloquium
ESB 2012
A Class of Polytopes with a Remarkable Volume Formula
ESB 2012
Fri 3 Nov 2017, 3:00pm-4:00pm

Abstract

TBA

Note for Attendees

Light refreshments will be served at 2:45pm in ESB 4133, the PIMS Lounge before this colloquium.
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Aaron Palmer
UBC
Tue 7 Nov 2017, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
Optimal Stopping with a Probabilistic Constraint
ESB 2012
Tue 7 Nov 2017, 3:30pm-4:30pm

Abstract

Optimal stopping problems can be viewed as a problem to calculate
the space and time dependent value function, which solves a nonlinear, possibly
non-smooth and degenerate, parabolic PDE known as an Hamilton-Jacobi-Bellman
(HJB) equation.  These equations are well understood using the theory of
viscosity solutions, and the optimal stopping policy can be retrieved when
there is some regularity and non-degeneracy of solution.
 
The HJB equation is commonly derived from a dynamic programming principle
(DPP). After adding a probabilistic constraint, the optimal policies no longer
satisfy this DPP.  Instead, we can reach the HJB equation by a method related
to optimal transportation, and  recover a DPP for a Lagrangian-relaxation of
the problem.  The resulting HJB equation remains coupled through the constraint
with the optimal policy (and another parabolic PDE).  Solving the HJB and
recovery of the optimal stopping policy is aided by considering the
``piecewise-monotonic’' structure of the stopping set.
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Foster Tom
UBC
Tue 7 Nov 2017, 4:00pm
Discrete Math Seminar
ESB 4127
TBD
ESB 4127
Tue 7 Nov 2017, 4:00pm-5:00pm

Abstract

 
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University of California, Irvine
Wed 8 Nov 2017, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)
ESB 4133 (PIMS Lounge)
Wed 8 Nov 2017, 3:15pm-4:15pm

Abstract

 

Note for Attendees


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Emory University
Thu 9 Nov 2017, 3:30pm
Number Theory Seminar
Math 126
Polya’s Program for the Riemann Hypothesis and Related Problems
Math 126
Thu 9 Nov 2017, 3:30pm-5:00pm

Abstract

In 1927 Polya  proved that the Riemann Hypothesis is equivalent to the hyperbolicity of Jensen polynomials for Riemann's Xi-function. This hyperbolicity has only been proved for degrees d=1, 2, 3. We prove the hyperbolicity of 100\% of the Jensen polynomials of every degree. We obtain a general theorem which models such polynomials by Hermite polynomials.
This theorem also allows us to prove a conjecture of Chen, Jia, and Wang on the partition function. This is joint work with Michael Griffin, Larry Rolen, and Don Zagier.
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UC Irvine
Sat 11 Nov 2017, 4:00pm
Algebraic Geometry Seminar
MATH 126
TBA
MATH 126
Sat 11 Nov 2017, 4:00pm-5:00pm

Abstract

 
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Wayne State University
Wed 15 Nov 2017, 3:15pm
Topology and related seminars
ESB 4133
ESB 4133
Wed 15 Nov 2017, 3:15pm-4:15pm

Abstract

 
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Université de Montréal
Fri 17 Nov 2017, 11:00am
Number Theory Seminar
MATX1118 (tentative)
TBA
MATX1118 (tentative)
Fri 17 Nov 2017, 11:00am-12:00pm

Abstract


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Yaniv Plan
UBC
Fri 17 Nov 2017, 3:00pm SPECIAL
ESB 2012
PIMS-UBC Distinguished Colloquium--TBA (for PIMS UBC Math Sciences prize)
ESB 2012
Fri 17 Nov 2017, 3:00pm-4:00pm

Details

 

Note for Attendees

Light refreshments will be served at 2:45pm in ESB 4133, the PIMS Lounge before this colloquium.
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Michal Kowalczyk
University of Chile
Tue 21 Nov 2017, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
Asymptotic stability for some nonlinear Klein-Gordon equations for odd perturbations in the energy space
ESB 2012
Tue 21 Nov 2017, 3:30pm-4:30pm

Abstract

 Showing asymptotic stability in one dimensional nonlinear Klein-Gordon equations is a notoriously difficult problem. In this talk I will describe an approach based on virial estimates which allows to prove it in case when only odd perturbations are allowed. In particular I will discuss asymptotic stability of the kink in the $\phi^4$ model.       
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University of Southern California
Wed 22 Nov 2017, 3:15pm
Topology and related seminars
ESB 4133
ESB 4133
Wed 22 Nov 2017, 3:15pm-4:15pm

Abstract

 
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Université Paris-Saclay
Wed 29 Nov 2017, 3:15pm SPECIAL
Department Colloquium
ESB 2012
TBA
ESB 2012
Wed 29 Nov 2017, 3:15pm-4:15am

Abstract


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Courant Institute, NYU
Fri 1 Dec 2017, 3:00pm SPECIAL
Department Colloquium
ESB 2012
PIMS-UBC Distinguished Colloquium--TBA
ESB 2012
Fri 1 Dec 2017, 3:00pm-4:00pm

Abstract

 

Note for Attendees

Light refreshments will be served at 2:45pm in ESB 4133, the PIMS Lounge before this colloquium.
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University of Lethbridge
Thu 4 Jan 2018, 3:30pm
Number Theory Seminar
TBA
TBA
TBA
Thu 4 Jan 2018, 3:30pm-10:00am

Abstract


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Harvard
Thu 25 Jan 2018, 4:00pm SPECIAL
TBA
TBA
TBA
Thu 25 Jan 2018, 4:00pm-5:00pm

Details


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Umberto Zannier
SNS, Pisa
Fri 2 Mar 2018, 3:00pm SPECIAL
Department Colloquium
ESB2012
PIMS-UBC Distinguished Colloquium--TBA
ESB2012
Fri 2 Mar 2018, 3:00pm-4:00pm

Abstract

 

Note for Attendees

Refreshments will be served in ESB 4133 from 2:45 p.m.-3:00 p.m.
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Jean-Marc Deshouillers
University of Bordeaux
Thu 29 Mar 2018, 3:30pm
Number Theory Seminar
TBA
Thu 29 Mar 2018, 3:30pm-5:00pm

Abstract


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University of Oxford
Fri 6 Apr 2018, 3:00pm
Department Colloquium
ESB 2012
PIMS-UBC Distinguished Colloquium--TBA
ESB 2012
Fri 6 Apr 2018, 3:00pm-4:00pm

Abstract

 

Note for Attendees

Light refreshments will be served at 2:45pm in ESB 4133, the PIMS Lounge before this colloquium.
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