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 Events
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, 2:15pm-3:15pm

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, 3:30pm-4:30pm

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 Bruhat-Tits 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 Bruhat-Tits 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 (PIMS-UBC Distinguished Colloquium)
ESB 2012 (PIMS)
Fri 19 Sep 2014, 3:00pm-4:00pm

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 "high-dimensional 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 p-adic 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, 3:00pm-4:00pm

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, 3:00pm-4:00pm

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 non-academic 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. 

Note for Attendees

John Stockie is the winner of the 2014 CAIMS/Mprime Industrial Mathematics Prize. 
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Baptiste Devyver
UBC
Tue 23 Sep 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
TBA
ESB 2012
Tue 23 Sep 2014, 3:30pm-4:30pm

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 long-range jumps
ESB 2012
Wed 24 Sep 2014, 3:00pm-4:00pm

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 nearest-neighbor 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 heat-kernel 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 long-range 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 long-range percolation graphs with exponents larger than d+2 in all d >= 2, provided all nearest-neighbor 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, 3:15pm-4:15pm

Abstract

 
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UBC
Thu 25 Sep 2014, 12:30pm
Graduate Student Seminar
Math 225
TBA
Math 225
Thu 25 Sep 2014, 12:30pm-2:00pm

Abstract

 TBA

Note for Attendees

 Pizza and pop will be provided.
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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, 3:30pm-4:30pm

Abstract


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UBC
Fri 26 Sep 2014, 3:00pm
Department Colloquium
Mathematics Annex 1100
The Dynamical Mordell-Lang problem
Mathematics Annex 1100
Fri 26 Sep 2014, 3:00pm-4:00pm

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 self-map 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 n-th 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, 3:00pm-4:00pm

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 hoped-for 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, 2:30pm-3:30pm

Abstract

This talk concerns the geometry of shrinking Ricci solitons, a class of self-similar 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 Cergy-Pontoise
Tue 30 Sep 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
TBA
Tue 30 Sep 2014, 3:30pm-4:30am
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Hong Kong University of Science and Technology
Wed 1 Oct 2014, 3:00pm
Probability Seminar
ESB 2012
Solving the high-dimensional Markowitz Optimization Problem: a tale of sparse solutions
ESB 2012
Wed 1 Oct 2014, 3:00pm-4:00am

Abstract

We consider the high-dimensional 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 high-dimensional setting. We further conduct simulation and empirical studies to compare our method with some benchmark methods, including the equally weighted portfolio, the bootstrap-corrected method by Bai et al. (2009) and the covariance-shrinkage 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, 3:15pm-4:15pm

Abstract

 
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Université Paris-Sud
Thu 2 Oct 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
TBA
TBA
TBA
Thu 2 Oct 2014, 3:30pm-4:30pm

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, 3:30pm-4:30pm

Abstract

An old conjecture of Lang (for elliptic curves) generalized by Silverman, asserts that the Néron-Tate 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, 3:00pm-4:00pm

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, 3:30pm-4:30pm

Abstract

 
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Simon Fraser University
Wed 8 Oct 2014, 3:00pm
Probability Seminar
ESB 2012
Modelling and simulating systems with state-dependent diffusion
ESB 2012
Wed 8 Oct 2014, 3:00pm-4:00am

Abstract

We propose a framework for modelling stochastic systems with state-dependent diffusion coefficients. Rather than specifying dynamics through a state-dependent drift and diffusion coefficients, assuming detailed balance we specify an equilibrium probability density and a state-dependent 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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Dick Gross
Thu 9 Oct 2014, 3:30pm
Number Theory Seminar
room MATH 126
TBA
room MATH 126
Thu 9 Oct 2014, 3:30pm-4:30pm

Abstract

 
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Harvard University
Fri 10 Oct 2014, 3:00pm
Department Colloquium
ESB 2012 (PIMS) Time and date to be confirmed
PIMS-UBC Distinguished Colloquium, TitleTBA
ESB 2012 (PIMS) Time and date to be confirmed
Fri 10 Oct 2014, 3:00pm-4:00pm

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, 3:30pm-4:30pm

Abstract

 
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TBA
Thu 16 Oct 2014, 3:30pm
Number Theory Seminar
room MATH 126
room MATH 126
Thu 16 Oct 2014, 3:30pm-4:30pm

Abstract

 
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Tingting Huan
UBC
Tue 21 Oct 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
TBA
ESB 2012
Tue 21 Oct 2014, 3:30pm-4:30pm

Abstract

 
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Avi Kulkarni
SFU
Thu 23 Oct 2014, 3:30pm
Number Theory Seminar
room MATH 126
TBA
room MATH 126
Thu 23 Oct 2014, 3:30pm-4:30pm

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, 3:30pm-4:30pm

Abstract

 
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Univeristy of Michigan
Fri 31 Oct 2014, 3:00pm
Department Colloquium
ESB 2012 (PIMS)
PIMS-IAM-UBC distinguished colloquium
ESB 2012 (PIMS)
Fri 31 Oct 2014, 3:00pm-4:00pm

Abstract


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Justin Chan
SFU
Tue 4 Nov 2014, 4:00pm
Discrete Math Seminar
ESB 4133
An infinite family of inv-Wilf-equivalent permutation pairs
ESB 4133
Tue 4 Nov 2014, 4:00pm-5:00pm

Abstract

Wilf-equivalence is one of the central concepts of pattern-avoiding permutations, and has been studied for more than thirty years. The two known infi nite families of Wilf-equivalent permutation pairs, due to Stankova-West and Backelin-West-Xin, both satisfy the stronger condition of shape-Wilf-equivalence. Dokos et al. recently studied a di fferent strengthening of Wilf-equivalence called inv-Wilf-equivalence, which takes account of the inversion number of a permutation. They conjectured that all inv-Wilf-equivalent permutation pairs arise from trivial symmetries. We disprove this conjecture by constructing an infi nite family of counterexamples derived from the permutation pair (231) and (312). The key to this construction is to generalize simultaneously the concepts of shape-Wilf-equivalence and inv-Wilf-equivalence. A further consequence is a proof of the recent Baxter-Jaggard conjecture on even-shape-Wilf-equivalent permutation pairs.
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Uriya First
UBC
Thu 6 Nov 2014, 3:30pm
Number Theory Seminar
room MATH 126
TBA
room MATH 126
Thu 6 Nov 2014, 3:30pm-4:30pm

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, 1:30pm-2:30pm

Abstract

 TBA
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TBA
Thu 13 Nov 2014, 3:30pm
Number Theory Seminar
room MATH 126
room MATH 126
Thu 13 Nov 2014, 3:30pm-4:30pm

Abstract

 
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TBA (reserved)
Fri 14 Nov 2014, 3:00pm
Department Colloquium
TBA
TBA
TBA
Fri 14 Nov 2014, 3:00pm-4:00pm

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, 3:00pm-4:00pm

Abstract

 TBA
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TBA
Thu 20 Nov 2014, 3:30pm
Number Theory Seminar
room MATH 126
room MATH 126
Thu 20 Nov 2014, 3:30pm-4:30pm

Abstract

 
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TBA
Thu 27 Nov 2014, 3:30pm
Number Theory Seminar
room MATH 126
room MATH 126
Thu 27 Nov 2014, 3:30pm-4:30pm

Abstract

 
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Caltech
Fri 30 Jan 2015, 3:00pm
Department Colloquium
ESB 2012 (PIMS) TBA (time and date to be confirmed)
PIMS-UBC distinguished colloquium
ESB 2012 (PIMS) TBA (time and date to be confirmed)
Fri 30 Jan 2015, 3:00pm-4:00pm

Abstract


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Brown University
Fri 13 Mar 2015, 3:00pm
Department Colloquium
ESB 2012 (PIMS)
PIMS-UBC Distinguished Colloquium, TitleTBA
ESB 2012 (PIMS)
Fri 13 Mar 2015, 3:00pm-4:00pm

Abstract


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