National University of Mexico

Thu 18 Sep 2014, 2:15pm
SPECIAL
Topology and related seminars
ESB 4133

On the Chern classes of singular varieties

ESB 4133
Thu 18 Sep 2014, 2:15pm3:15pm
Abstract
Chern classes of complex manifolds play a key role in geometry and topology. In this talk we shall discuss how these classes extend to singular varieties. In fact there are various possible extensions, depending on which properties of Chern classes you want to preserve. This is closely related to asking who plays the role of the tangent bundle at the singular points (where there is no tangent bundle).
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Hebrew University of Jerusalem

Thu 18 Sep 2014, 3:30pm
Number Theory Seminar
room MATH 126

From Ramanujan graphs to Ramanujan complexes

room MATH 126
Thu 18 Sep 2014, 3:30pm4:30pm
Abstract
Ramanujan graphs are optimal expanders (from spectral point of view). Explicit constructions of such graphs were given in the 80's as quotients of the BruhatTits tree associated with GL(2) over a local field F, by suitable congruence subgroups. The spectral bounds were proved using works of Hecke, Deligne and Drinfeld on the "Ramanujan conjecture" in the theory of automorphic forms. The work of Lafforgue, extending Drinfeld from GL(2) to GL(n), opened the door for the construction of Ramanujan complexes as quotients of the BruhatTits buildings. This gives finite simplical complxes which on one hand are "random like" and at the same time have strong symmetries. Recently various applications have been found in combinatorics, coding theory and in relation to Gromov's overlapping properties. We will describe these developments and give some details on recent applications.
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Hebrew University of Jerusalem

Fri 19 Sep 2014, 3:00pm
Department Colloquium
ESB 2012 (PIMS)

High dimensional expanders and Ramanujan complexes (PIMSUBC Distinguished Colloquium)

ESB 2012 (PIMS)
Fri 19 Sep 2014, 3:00pm4:00pm
Abstract
Expander graphs have played, in the last few decades, an important role in computer science, and in the last decade, also in pure mathematics. In recent years a theory of "highdimensional expanders" is starting to emerge  i.e., simplical complexes which generalize various properties of expander graphs. This has some geometric motivations (led by Gromov) and combinatorial ones (started by Linial and Meshulam). The talk will survey the various directions of research and their applications, as well as potential applications in math and CS. Some of these lead to questions about buildings and representation theory of padic groups.
We will survey the work of a number of people. The works of the speaker in this direction are with various subsets of { S. Evra, K. Golubev, T. Kaufman, D. Kazhdan , R. Meshulam, S. Mozes }
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Bonn

Mon 22 Sep 2014, 3:00pm
CRG Geometry and Physics Seminar
ESB 4127 (host: UBC)

TBA

ESB 4127 (host: UBC)
Mon 22 Sep 2014, 3:00pm4:00pm
Abstract
TBA
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Mathematics, SFU

Mon 22 Sep 2014, 3:00pm
Institute of Applied Mathematics
LSK 460

Challenges and Opportunities in ”Mathematics for Industry”

LSK 460
Mon 22 Sep 2014, 3:00pm4:00pm
Abstract
Industrial mathematics is a field that spans a broad spectrum of activity ranging from applied R&D performed by mathematicians employed in industry, to purely academic research projects undertaken by university mathematics professors. In this talk, I will survey several research projects I have been involved with that fall under the heading of what I’ll call ”mathematics *for* industry”, which relates specifically to direct collaborations between university mathematicians and nonacademic partner organizations. These projects encompass a diverse collection of mathematical techniques (ranging from simple algebra to partial differential equations, finite volume methods, inverse problems and homogenization theory) as well as applications from many scientific disciplines (such as fluid mechanics, image processing, atmospheric science and plant biology). In the process, I will attempt to characterize the job of an industrial mathematician and to identify the qualities and skills that are most desirable for anyone interested in making significant contributions to research at the interface between university and industry. I also hope to convince you that industrial collaborations can be a rich source of challenging and novel mathematical problems for academic mathematicians.
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UBC

Tue 23 Sep 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012

TBA

ESB 2012
Tue 23 Sep 2014, 3:30pm4:30pm
Abstract
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Kyoto University

Wed 24 Sep 2014, 3:00pm
Probability Seminar
ESB 2012

Quenched Invariance Principle for a class of random conductance models with longrange jumps

ESB 2012
Wed 24 Sep 2014, 3:00pm4:00pm
Abstract
We study random walks on Z^d among random conductances {C_{xy}: x,y in Z^d} that permit jumps of arbitrary length. Apart from joint ergodicity with respect to shifts, we assume only that the nearestneighbor conductances are uniformly positive and that sum_{x in Z^d} C_{0x} x^2 is integrable.
Our focus is on the Quenched Invariance Principle (QIP) which we establish in all d >= 3 by a combination of corrector methods and heatkernel technology. We also show that our class contains examples where the corrector is not sublinear everywhere and yet the QIP holds. Thus, although the recent work of Andres, Slowik and Deuschel can be extended to longrange models, it cannot cover all cases for which the QIP is conjectured to hold. Notwithstanding, a combination of their methods with ours proves the QIP for random walks on longrange percolation graphs with exponents larger than d+2 in all d >= 2, provided all nearestneighbor edges are present.
This is an ongoing joint work with Marek Biskup (UCLA).
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UBC

Wed 24 Sep 2014, 3:15pm
Topology and related seminars
ESB 4133

TBA

ESB 4133
Wed 24 Sep 2014, 3:15pm4:15pm
Abstract
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UBC

Thu 25 Sep 2014, 12:30pm
Graduate Student Seminar
Math 225

TBA

Math 225
Thu 25 Sep 2014, 12:30pm2:00pm
Abstract
TBA
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UBC

Thu 25 Sep 2014, 3:30pm
Number Theory Seminar
room MATH 126

Primitive and doubly primitive divisors in dynamical sequences

room MATH 126
Thu 25 Sep 2014, 3:30pm4:30pm
Abstract
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UBC

Fri 26 Sep 2014, 3:00pm
Department Colloquium
Mathematics Annex 1100

The Dynamical MordellLang problem

Mathematics Annex 1100
Fri 26 Sep 2014, 3:00pm4:00pm
Abstract
A space X is called Noetherian if there is no infinite descending chain of closed subsets of X. Let X be a Noetherian space, let f be a continuous selfmap on X, let Y be a closed subset of X, and let x be a point in X. We show that the set containing all positive integers n such that the nth iterate of x under f lands in Y is a union of at most finitely many arithmetic progressions along with a set of Banach density 0. This result has various consequences from the distribution of zeros in recurrence sequences to questions in arithmetic geometry.
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Stanford

Mon 29 Sep 2014, 3:00pm
CRG Geometry and Physics Seminar
ESB 4127 (host: UBC)

Stabilization of discriminants in the Grothendieck ring

ESB 4127 (host: UBC)
Mon 29 Sep 2014, 3:00pm4:00pm
Abstract
We consider the ``limiting behavior'' of {\em discriminants}, by which we mean informally the closure of the locus in some parameter space of some type of object where the objects have certain singularities. We focus on the space of partially labeled points on a variety X, and linear systems on X. These are connected  we use the first to understand the second. We describe their classes in the "ring of motives", as the number of points gets large, or as the line bundle gets very positive. They stabilize in an appropriate sense, and their stabilization can be described in terms of the motivic zeta values. The results extend parallel results in both arithmetic and topology. I will also
present a conjecture (on ``motivic stabilization of symmetric powers'') suggested by our work. Although it is true in important cases, Daniel Litt has shown that it contradicts other hopedfor statements. This is joint work with Melanie Wood.
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University of Minnesota

Tue 30 Sep 2014, 2:30pm
Diff. Geom, Math. Phys., PDE Seminar

Geometry of shrinking Ricci solitons

Tue 30 Sep 2014, 2:30pm3:30pm
Abstract
This talk concerns the geometry of shrinking Ricci solitons, a class of selfsimilar solutions to the
Ricci flows. We plan to provide some general background results and explain a recent work with Ovidiu Munteanu
on the curvature estimates of four dimensional solitons
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Universite de CergyPontoise

Tue 30 Sep 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar

TBA

Tue 30 Sep 2014, 3:30pm4:30am
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Hong Kong University of Science and Technology

Wed 1 Oct 2014, 3:00pm
Probability Seminar
ESB 2012

Solving the highdimensional Markowitz Optimization Problem: a tale of sparse solutions

ESB 2012
Wed 1 Oct 2014, 3:00pm4:00am
Abstract
We consider the highdimensional Markowitz optimization problem. A new approach combining sparse regression and estimation of optimal returns based on random matrix theory is proposed to solve the problem. We prove that under some sparsity assumptions on the underlying optimal portfolio, our novel approach asymptotically yields the theoretical optimal return, and in the meanwhile satisfies the risk constraint. To the best of our knowledge, this is the first method that can achieve these two goals simultaneously in the highdimensional setting. We further conduct simulation and empirical studies to compare our method with some benchmark methods, including the equally weighted portfolio, the bootstrapcorrected method by Bai et al. (2009) and the covarianceshrinkage method by Ledoit and Wolf (2004). The results demonstrate substantial advantage of our method, which attains high level of returns while keeping the risk well controlled by the given constraint.
Based on joint work with Mengmeng Ao and Yingying Li.
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UBC

Wed 1 Oct 2014, 3:15pm
Topology and related seminars
ESB 4133


ESB 4133
Wed 1 Oct 2014, 3:15pm4:15pm
Abstract
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Université ParisSud

Thu 2 Oct 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
TBA

TBA

TBA
Thu 2 Oct 2014, 3:30pm4:30pm
Abstract
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Université Pierre et Marie Curie

Thu 2 Oct 2014, 3:30pm
Number Theory Seminar
room MATH 126

Points of small height on abelian varieties over function fields

room MATH 126
Thu 2 Oct 2014, 3:30pm4:30pm
Abstract
An old conjecture of Lang (for elliptic curves) generalized by Silverman, asserts that the NéronTate height of a rational point of an abelian variety defined over a number field can be bounded below linearly in terms of the Faltings height of the underlying abelian variety. We shall explore the function field analogue of this problem.
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UBC

Fri 3 Oct 2014, 3:00pm
Department Colloquium
MATH Annex 1100

TBA

MATH Annex 1100
Fri 3 Oct 2014, 3:00pm4:00pm
Abstract
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UBC

Tue 7 Oct 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012

TBA

ESB 2012
Tue 7 Oct 2014, 3:30pm4:30pm
Abstract
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Simon Fraser University

Wed 8 Oct 2014, 3:00pm
Probability Seminar
ESB 2012

Modelling and simulating systems with statedependent diffusion

ESB 2012
Wed 8 Oct 2014, 3:00pm4:00am
Abstract
We propose a framework for modelling stochastic systems with statedependent diffusion coefficients. Rather than specifying dynamics through a statedependent drift and diffusion coefficients, assuming detailed balance we specify an equilibrium probability density and a statedependent diffusion coefficient. We argue that our framework is more natural from the modelling point of view and has a distinct advantage in situations where either the equilibrium probability density or the diffusion coefficient is discontinuous. We introduce a numerical method for simulating dynamics in our framework that samples from the equilibrium probability density exactly and elegantly handles discontinuities in the coefficients. This is joint work with Xin Yang.
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Thu 9 Oct 2014, 3:30pm
Number Theory Seminar
room MATH 126

TBA

room MATH 126
Thu 9 Oct 2014, 3:30pm4:30pm
Abstract
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Harvard University

Fri 10 Oct 2014, 3:00pm
Department Colloquium
ESB 2012 (PIMS) Time and date to be confirmed

PIMSUBC Distinguished Colloquium, TitleTBA

ESB 2012 (PIMS) Time and date to be confirmed
Fri 10 Oct 2014, 3:00pm4:00pm
Abstract
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Toulouse

Tue 14 Oct 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012

TBA

ESB 2012
Tue 14 Oct 2014, 3:30pm4:30pm
Abstract
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Thu 16 Oct 2014, 3:30pm
Number Theory Seminar
room MATH 126


room MATH 126
Thu 16 Oct 2014, 3:30pm4:30pm
Abstract
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UBC

Tue 21 Oct 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012

TBA

ESB 2012
Tue 21 Oct 2014, 3:30pm4:30pm
Abstract
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SFU

Thu 23 Oct 2014, 3:30pm
Number Theory Seminar
room MATH 126

TBA

room MATH 126
Thu 23 Oct 2014, 3:30pm4:30pm
Abstract
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Emory University

Thu 30 Oct 2014, 3:30pm
Number Theory Seminar
room MATH 126

TBA

room MATH 126
Thu 30 Oct 2014, 3:30pm4:30pm
Abstract
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Univeristy of Michigan

Fri 31 Oct 2014, 3:00pm
Department Colloquium
ESB 2012 (PIMS)

PIMSIAMUBC distinguished colloquium

ESB 2012 (PIMS)
Fri 31 Oct 2014, 3:00pm4:00pm
Abstract
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SFU

Tue 4 Nov 2014, 4:00pm
Discrete Math Seminar
ESB 4133

An infinite family of invWilfequivalent permutation pairs

ESB 4133
Tue 4 Nov 2014, 4:00pm5:00pm
Abstract
Wilfequivalence is one of the central concepts of patternavoiding permutations, and has been studied for more than thirty years. The two known infinite families of Wilfequivalent permutation pairs, due to StankovaWest and BackelinWestXin, both satisfy the stronger condition of shapeWilfequivalence. Dokos et al. recently studied a different strengthening of Wilfequivalence called invWilfequivalence, which takes account of the inversion number of a permutation. They conjectured that all invWilfequivalent permutation pairs arise from trivial symmetries. We disprove this conjecture by constructing an infinite family of counterexamples derived from the permutation pair (231) and (312). The key to this construction is to generalize simultaneously the concepts of shapeWilfequivalence and invWilfequivalence. A further consequence is a proof of the recent BaxterJaggard conjecture on evenshapeWilfequivalent permutation pairs.
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UBC

Thu 6 Nov 2014, 3:30pm
Number Theory Seminar
room MATH 126

TBA

room MATH 126
Thu 6 Nov 2014, 3:30pm4:30pm
Abstract
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Berkeley

Fri 7 Nov 2014, 1:30pm
CRG Geometry and Physics Seminar
ESB 4127 (host: UBC)

TBA

ESB 4127 (host: UBC)
Fri 7 Nov 2014, 1:30pm2:30pm
Abstract
TBA
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Thu 13 Nov 2014, 3:30pm
Number Theory Seminar
room MATH 126


room MATH 126
Thu 13 Nov 2014, 3:30pm4:30pm
Abstract
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Fri 14 Nov 2014, 3:00pm
Department Colloquium
TBA

TBA

TBA
Fri 14 Nov 2014, 3:00pm4:00pm
Abstract
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Jussieu

Mon 17 Nov 2014, 3:00pm
CRG Geometry and Physics Seminar
ESB 4127 (host: UBC)

TBA

ESB 4127 (host: UBC)
Mon 17 Nov 2014, 3:00pm4:00pm
Abstract
TBA
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Thu 20 Nov 2014, 3:30pm
Number Theory Seminar
room MATH 126


room MATH 126
Thu 20 Nov 2014, 3:30pm4:30pm
Abstract
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Thu 27 Nov 2014, 3:30pm
Number Theory Seminar
room MATH 126


room MATH 126
Thu 27 Nov 2014, 3:30pm4:30pm
Abstract
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Caltech

Fri 30 Jan 2015, 3:00pm
Department Colloquium
ESB 2012 (PIMS) TBA (time and date to be confirmed)

PIMSUBC distinguished colloquium

ESB 2012 (PIMS) TBA (time and date to be confirmed)
Fri 30 Jan 2015, 3:00pm4:00pm
Abstract
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Brown University

Fri 13 Mar 2015, 3:00pm
Department Colloquium
ESB 2012 (PIMS)

PIMSUBC Distinguished Colloquium, TitleTBA

ESB 2012 (PIMS)
Fri 13 Mar 2015, 3:00pm4:00pm
Abstract
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Note for Attendees
John Stockie is the winner of the 2014 CAIMS/Mprime Industrial Mathematics Prize.