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, 12:00pm1:00pm
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 groundbreaking 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 postdocs 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 highlevel 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, 3:00pm4:00pm
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.
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SNS Pisa

Mon 23 Oct 2017, 4:00pm
Algebraic Geometry Seminar
MATH 126

TBA

MATH 126
Mon 23 Oct 2017, 4:00pm5:00pm
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, 3:30pm4:30pm
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
nonrigidity results of Li Wang, and a new quasi local type inequality of
LuMiao. 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, 4:00pm5:00pm
Abstract
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UBC

Mon 30 Oct 2017, 4:00pm
Algebraic Geometry Seminar
MATH 126

TBA

MATH 126
Mon 30 Oct 2017, 4:00pm5:00pm
Abstract
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University of Alberta at Edmonton

Wed 1 Nov 2017, 3:00pm
Probability Seminar
ESB 2012

FeynmanKac formula for the stochastic heat equation driven by general Gaussian noises

ESB 2012
Wed 1 Nov 2017, 3:00pm4:00pm
Abstract
In this talk I will present some results on stochastic heat equations driven by a Gaussian noises. I will focus on FeynmanKac 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 socalled 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, 3:00pm4:00pm
Abstract
TBA
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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, 3:30pm4:30pm
Abstract
Optimal stopping problems can be viewed as a problem to calculate
the space and time dependent value function, which solves a nonlinear, possibly
nonsmooth and degenerate, parabolic PDE known as an HamiltonJacobiBellman
(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 nondegeneracy 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 Lagrangianrelaxation 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
``piecewisemonotonic’' structure of the stopping set.
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UBC

Tue 7 Nov 2017, 4:00pm
Discrete Math Seminar
ESB 4127

TBD

ESB 4127
Tue 7 Nov 2017, 4:00pm5:00pm
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, 3:15pm4:15pm
Abstract
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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, 3:30pm5:00pm
Abstract
In 1927 Polya proved that the Riemann Hypothesis is equivalent to the hyperbolicity of Jensen polynomials for Riemann's Xifunction. 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, 4:00pm5:00pm
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, 3:15pm4:15pm
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, 11:00am12:00pm
Abstract
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UBC

Fri 17 Nov 2017, 3:00pm
SPECIAL
ESB 2012

PIMSUBC Distinguished ColloquiumTBA (for PIMS UBC Math Sciences prize)

ESB 2012
Fri 17 Nov 2017, 3:00pm4:00pm
Details
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University of Chile

Tue 21 Nov 2017, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012

Asymptotic stability for some nonlinear KleinGordon equations for odd perturbations in the energy space

ESB 2012
Tue 21 Nov 2017, 3:30pm4:30pm
Abstract
Showing asymptotic stability in one dimensional nonlinear KleinGordon 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, 3:15pm4:15pm
Abstract
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Université ParisSaclay

Wed 29 Nov 2017, 3:15pm
SPECIAL
Department Colloquium
ESB 2012

TBA

ESB 2012
Wed 29 Nov 2017, 3:15pm4:15am
Abstract
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Courant Institute, NYU

Fri 1 Dec 2017, 3:00pm
SPECIAL
Department Colloquium
ESB 2012

PIMSUBC Distinguished ColloquiumTBA

ESB 2012
Fri 1 Dec 2017, 3:00pm4:00pm
Abstract
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University of Lethbridge

Thu 4 Jan 2018, 3:30pm
Number Theory Seminar
TBA

TBA

TBA
Thu 4 Jan 2018, 3:30pm10:00am
Abstract
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Harvard

Thu 25 Jan 2018, 4:00pm
SPECIAL
TBA

TBA

TBA
Thu 25 Jan 2018, 4:00pm5:00pm
Details
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SNS, Pisa

Fri 2 Mar 2018, 3:00pm
SPECIAL
Department Colloquium
ESB2012

PIMSUBC Distinguished ColloquiumTBA

ESB2012
Fri 2 Mar 2018, 3:00pm4:00pm
Abstract
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University of Bordeaux

Thu 29 Mar 2018, 3:30pm
Number Theory Seminar

TBA

Thu 29 Mar 2018, 3:30pm5:00pm
Abstract
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University of Oxford

Fri 6 Apr 2018, 3:00pm
Department Colloquium
ESB 2012

PIMSUBC Distinguished ColloquiumTBA

ESB 2012
Fri 6 Apr 2018, 3:00pm4:00pm
Abstract
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Note for Attendees
Light refreshments will be served at 2:45pm in ESB 4133, the PIMS Lounge before this colloquium.