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 Events
Mathematics, Guelph
Mon 3 Nov 2014, 3:00pm SPECIAL
Institute of Applied Mathematics
LSK 460
The Good, the Bad, and the Ugly: From Biofilms to Mathematics and Back Again
LSK 460
Mon 3 Nov 2014, 3:00pm-4:00pm

Abstract

Bacterial biofilms are microbial depositions that form on immersed surfaces wherever environmental conditions sustain bacterial growth. They have been called the most successful life form on Earth and cities of microbes. Biofilms have important applications in environmental engineering, but are detrimental in a medical or industrial context. They have been characterised as both, spatially structured microbial populations, and as mechanical objects. Life in biofilm communities significantly differs from life in planktonic cultures. This is reflected in the complexity of mathematical models of biofilms that are essentially more involved than models of suspended microbial communities. In this talk I will focus on a class of highly degenerate diffusion-reaction biofilm models. In its simplest form this includes simultaneously two nonlinear diffusion effects: (i) a porous medium equation like degeneracy when the dependent variable biomass density vanishes, and (ii) a super-diffusion singularity when it attains its {\it a priori} known upper bound. I will summarize some analytical (well-posedness) results, and discuss applications of the model to answer questions about biofilms by numerical simulations. I will hereby focus on the contribution of mathematical models (this and others) to understand the formation of cluster-and-channel biofilm architectures, and I will illustrate how our model framework, extended by a model of bacterial communication by quorum sensing, can be used to shed light on the transition from an initial mode of biofilm colonization to a protected mode of biofilm growth.
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UBC
Mon 3 Nov 2014, 3:00pm
Harmonic Analysis Seminar
Math 204
Restriction theory and quadratic equations in dense variables
Math 204
Mon 3 Nov 2014, 3:00pm-4:00pm

Abstract

We are interested in the problem of solving a translation-invariant linear equation in a dense subset of the squares. We focus on the quality of density bounds, and we explain how the efficient energy increment method developed by Heath-Brown and Szemeredi for Roth's theorem can be adapted to this problem. A key tool in the process is a restriction estimate of Bourgain for lattice sets, and we discuss its role in our density increment strategy.
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Kyoto University
Tue 4 Nov 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
TBA
ESB 2012
Tue 4 Nov 2014, 3:30pm-4:30pm

Abstract

 
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Justin Chan
SFU
Tue 4 Nov 2014, 4:00pm
Discrete Math Seminar
ESB 4127
An infinite family of inv-Wilf-equivalent permutation pairs
ESB 4127
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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MIT
Wed 5 Nov 2014, 3:00pm SPECIAL
Discrete Math Seminar / Harmonic Analysis Seminar
MATX1118
On geometric incidences
MATX1118
Wed 5 Nov 2014, 3:00pm-4:00pm

Abstract

 
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York University
Wed 5 Nov 2014, 3:10pm
Probability Seminar
ESB 2012
Random walk in non-elliptic random environments
ESB 2012
Wed 5 Nov 2014, 3:10pm-4:10pm

Abstract

Much of the literature on random walk in random environment assumes uniformly ellipticity, i.e., that nearest neighbour steps have probabilities bounded away from zero. I’ll describe some work with Mark Holmes (Univ. of Auckland) in which we relax this assumption, and allow some such steps to be forbidden. This leads naturally to percolation models, using which one can in some cases prove ballisticity of the random walks (existence of non-zero asymptotic speeds).
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Mike Wakin
Colorado School of Mines
Thu 6 Nov 2014, 12:00pm
Mathematics of Information and Applications Seminar
4133 ESB (PIMS lounge)
The Sketched SVD and Applications in Structural Health Monitoring
4133 ESB (PIMS lounge)
Thu 6 Nov 2014, 12:00pm-1:00pm

Abstract

We present a simple technique for estimating parts of the Singular Value Decomposition (SVD) of a data matrix from a small randomly compressed "sketch" of that matrix. In sensor network settings--where each column of the data matrix comes from a separate sensor--the sketch can be assembled using operations local to each sensor. As an application of this work, we consider the problem of Structural Health Monitoring (SHM). SHM systems are critical for monitoring aging infrastructure (such as buildings or bridges) in a cost-effective manner. Such systems typically involve collections of battery-operated wireless sensors that sample vibration data over time. After the data is transmitted to a central node, modal analysis can be used to detect damage in the structure. We propose and study three frameworks for Compressive Sensing (CS) in SHM systems; these methods are intended to minimize power consumption by allowing the data to be sampled and/or transmitted more efficiently. At the central node, all of these frameworks involve a very simple technique for estimating the structure's mode shapes without requiring a traditional CS reconstruction of the vibration signals; all that is needed is to compute a simple SVD. We support our proposed techniques theoretically and using simulations based on synthetic and real data. This project is joint work with Anna Gilbert and Jae Young Park.
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UBC
Thu 6 Nov 2014, 12:30pm
Graduate Student Seminar
Math 225
Supersymmetric integration
Math 225
Thu 6 Nov 2014, 12:30pm-1:45pm

Abstract

We begin by defining the Grassmann integral of a function of both commuting ("bosonic") and anti-commuting ("fermionic") variables. An important example is the mixed bosonic-fermionic ("supersymmetric") Gaussian integral, which exhibits a surprising self-normalization property. Time permitting, we will mention applications of the Grassmann integral to the representation of self-avoiding walk as a supersymmetric quantum field theory.
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Yariv Mizrahi
Thu 6 Nov 2014, 12:30pm SPECIAL
One Time Event
Room 200 of the Graduate Student Centre
Doctoral Exams
Room 200 of the Graduate Student Centre
Thu 6 Nov 2014, 12:30pm-2:30pm

Details

ABSTRACT We introduce a new class of parallel parameter learning algorithms for Markov random fields (MRFs) with untied parameters, which are efficient for a large class of practical models. The algorithms parallelize naturally over cliques and, for graphs of bounded degree, have complexity that is linear in the number of cliques. We refer to these algorithms with the acronym LAP, which stands for Linear And Parallel. Unlike their competitors, the marginal versions of the proposed algorithms are fully parallel and for log-linear models they are also data efficient, requiring only the local sufficient statistics of the data to estimate parameters. LAP algorithms are ideal for parameter learning in big graphs and big data applications. The correctness of the newly proposed algorithms relies heavily on the existence and uniqueness of the normalized potential representation of an MRF. We capitalize on this theoretical result to develop a new theory of correctness and consistency of LAP estimators corresponding to different local graph neighborhoods. This theory also establishes a general condition on composite likelihood decompositions of MRFs that guarantees the global consistency of distributed estimators, provided the local estimators are consistent. We introduce a conditional variant of LAP that enables us to attack parameter estimation of fully observed models of arbitrary connectivity, including fully connected Boltzmann distributions. We show consistency for this distributed estimator, and relate it to distributed pseudo-likelihood estimators. Finally, for linear and non-linear inverse problems with a sparse forward operator, we present a new algorithm, named iLAP, which decomposes the inverse problem into a set of smaller dimensional inverse problems that can be solved independently.
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Uriya First
UBC
Thu 6 Nov 2014, 3:30pm
Number Theory Seminar
room MATH 126
Rational isomorphism of quadratic forms and related objects
room MATH 126
Thu 6 Nov 2014, 3:30pm-4:30pm

Abstract

Let R be a discrete valuation ring with fraction field F. Two algebraic objects (say, quadratic forms) defined over R are said to be rationally isomorphic if they become isomorphic after extending scalars to F. In the case of unimodular quadratic forms, it is a classical result that rational isomorphism is equivalent to isomorphism. This has been recently extended to "almost umimodular" forms by Auel, Parimala and Suresh. I will present further generalizations to related objects: hermitian forms over involutary R-algebras, quadratic spaces equipped with a group action ("G-forms"), and systems of quadratic forms. The results can be regarded as versions of the Grothendieck–Serre conjecture for certain non-reductive groups. (Joint work with Eva Bayer–Fluckiger.)
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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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UBC
Fri 7 Nov 2014, 3:00pm
Department Colloquium
MATX 1100
A mysterious 3/4 and happy 1/2
MATX 1100
Fri 7 Nov 2014, 3:00pm-4:00pm

Abstract

I will discuss: 1. A new problem concerning monotone subsequences in random data;  2. Several approaches towards its solution;  3. Relations to some old problems from analysis, Ramsey theory and even probability. Based on work with Louigi Adarrio-Berry, Guillaume Chapuy, Luc Devroye, Gabor Lugosi, Neil Olver, Yuval Peres and Richard Balka.

Note for Attendees

Refreshments will be served at 2:45pm in the Math Lounge area, MATH 125 before the colloquium.
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UBC
Mon 10 Nov 2014, 3:00pm
CRG Geometry and Physics Seminar
ESB 4127 (host: UBC)
Versal actions with a twist
ESB 4127 (host: UBC)
Mon 10 Nov 2014, 3:00pm-4:00pm

Abstract

The term “versal” is best understood by subtracting “unique” from both sides of the formula

Universal = unique + versal.

In this talk based on joint work with Alex Duncan, I will discuss competing notions of versality for the action of an algebraic group G on an algebraic variety X and relate these notions to properties (such as existence and density) of rational points on twisted forms of X. I will then present examples, where this relationship can be used to prove that certain group actons are versal or, conversely, that certain varieties have rational points.

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UAlberta
Wed 12 Nov 2014, 3:00pm
CRG Geometry and Physics Seminar
ESB 4127 (host: UAlberta)
TBA
ESB 4127 (host: UAlberta)
Wed 12 Nov 2014, 3:00pm-4:00pm

Abstract

 TBA
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UBC
Wed 12 Nov 2014, 3:15pm
Topology and related seminars
ESB 4133
TBA
ESB 4133
Wed 12 Nov 2014, 3:15pm-4:15pm
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Deanna Needell
Thu 13 Nov 2014, 12:00pm
One Time Event
4133 ESB (PIMS lounge)
TBA
4133 ESB (PIMS lounge)
Thu 13 Nov 2014, 12:00pm-1:00pm

Details

 
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Morningside Center of Mathematics and Purdue
Thu 13 Nov 2014, 3:30pm
Number Theory Seminar
room MATH 126
Introduction to Mochizuki's works on inter-universal Teichmuller theory
room MATH 126
Thu 13 Nov 2014, 3:30pm-4:30pm

Abstract

Inter-universal Teichmuller theory, as developed by Mochizuki in the past decade, is an analogue for number fields of the classical Teichmuller theory, and also of the p-adic Teichmuller theory of Mochizuki. In this theory, the ring structure of a number field is subject to non-ring theoretic deformation. Absolute anabelian geometry, a refinement of anabelian geometry, plays a crucial role in inter-universal Teichmuller theory. In this talk, we will try to give an introduction to these ideas.
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UC Berkeley
Fri 14 Nov 2014, 3:00pm
Department Colloquium
MATX 1100
The fundamental theorem of arithmetic for metric measure spaces
MATX 1100
Fri 14 Nov 2014, 3:00pm-4:00pm

Abstract

A metric measure space (mms) is simply a complete, separable metric space equipped with a probability measure that has full support.  A fundamental insight of Gromov is that the space of such objects is much ``tamer'' than the space of complete, separable metric spaces per se because mms carry within themselves a canonical family of approximations by finite structures: one takes the random mms that arises from picking some number of points independently at random and equipping it with the induced metric and uniform probability measure.  A natural (commutative and associative) binary operation on the space of mms is defined by forming the Cartesian product of the two underlying sets equipped with the sum of the two metrics and the product of the two probability measures.  There is a corresponding notion of a prime  mms and an analogue of the fundamental theorem of arithmetic in the sense that any mms has a factorization into countably many prime mms which is unique up to the order of the factors.  Moreover,  a rich Fourier theory enables one to analyze convolutions of probability measures on the space of mms and obtain counterparts of classical results in the theory of infinitely divisible and stable probability measures on Euclidean spaces due to L\'evy, It\^o, Hin\u{c}in, and LePage.  This is joint work with Ilya Molchanov (Bern).

Note for Attendees

Refreshments will be served at 2:45pm in the Math Lounge area, MATH 125 before the colloquium.
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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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Weiwei Ao
UBC
Tue 18 Nov 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
TBA
ESB 2012
Tue 18 Nov 2014, 3:30pm-4:30pm

Abstract

 
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UBC
Wed 19 Nov 2014, 3:15pm
Topology and related seminars
ESB 4133
TBA
ESB 4133
Wed 19 Nov 2014, 3:15pm-4:15pm

Abstract

 
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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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The University of Auckland
Fri 21 Nov 2014, 3:00pm
Department Colloquium
Math Annex 1100
Reducing lectures, making students responsible, and offering semi-authentic mathematical experiences.
Math Annex 1100
Fri 21 Nov 2014, 3:00pm-4:00pm

Abstract

 In the Mathematics Department of The University of Auckland a major research project into undergraduate mathematics learning outcomes has required the development of three innovative ways to deliver undergraduate mathematics. One of these involves reducing lectures to less than one per week, handing responsibility for most of their mathematical learning to students using web or text resources. We then use the staff time saved to provide semi-authentic mathematical experiences in which students work in small groups for up to two hours at a time guided by a lecturer on open-ended mathematical situations. Such sessions require new teaching skills and new learning orientations. There is some evidence that we have made progress on the development of mathematical process skills.
Our research shows that, with our small trial groups, students perform at similar levels on the conventional assessments as do the students in the standard courses.

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UAlberta
Mon 24 Nov 2014, 3:00pm
CRG Geometry and Physics Seminar
ESB 4127 (host: UBC)
TBA
ESB 4127 (host: UBC)
Mon 24 Nov 2014, 3:00pm-4:00pm

Abstract

 TBA
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Monica Musso
Pont. Cat. Univ. Chile
Tue 25 Nov 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
Nondegeneracy of nonradial nodal solutions to Yamabe problem
ESB 2012
Tue 25 Nov 2014, 3:30pm-4:30pm

Abstract

 We prove the existence of a sequence of nondegenerate, in the sense of Duyckaerts-Kenig-Merle, nodal nonradial solutions to the critical Yamabe problem or stationary energy-critical wave equation.
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Tyler Helmuth
Tue 25 Nov 2014, 4:00pm SPECIAL
One Time Event
Graduate Student Center, Room 203
Doctoral Exam
Graduate Student Center, Room 203
Tue 25 Nov 2014, 4:00pm-6:30pm
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UAlberta
Wed 26 Nov 2014, 3:00pm
CRG Geometry and Physics Seminar
ESB 4127 (host: UAlberta)
TBA
ESB 4127 (host: UAlberta)
Wed 26 Nov 2014, 3:00pm-4:00pm

Abstract

 TBA
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MIT
Wed 26 Nov 2014, 3:15pm
Topology and related seminars
ESB 4133
ESB 4133
Wed 26 Nov 2014, 3:15pm-4:15pm
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Oxford University
Thu 27 Nov 2014, 3:30pm
Number Theory Seminar
room MATH 126
TBA
room MATH 126
Thu 27 Nov 2014, 3:30pm-4:30pm

Abstract

 
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TBA
Fri 28 Nov 2014, 3:00pm
Department Colloquium
MATX 1100
Graduate Research Award lecture
MATX 1100
Fri 28 Nov 2014, 3:00pm-4:00pm

Abstract


Note for Attendees


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Case Western
Wed 3 Dec 2014, 3:00pm
CRG Geometry and Physics Seminar
ESB 4127 (host: UAlberta)
TBA
ESB 4127 (host: UAlberta)
Wed 3 Dec 2014, 3:00pm-4:00pm

Abstract

 TBA
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Sat 10 Jan 2015, 9:00am SPECIAL
One Time Event
To Be Announced
Analysis - Qualifying Exams
To Be Announced
Sat 10 Jan 2015, 9:00am-12:00pm
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Sat 10 Jan 2015, 1:00pm SPECIAL
One Time Event
To Be Announced
Differential Equations - Qualifying Exams
To Be Announced
Sat 10 Jan 2015, 1:00pm-4:00pm
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Sat 10 Jan 2015, 1:00pm SPECIAL
One Time Event
To Be Announced Later
Algebra Qualifying Exams
To Be Announced Later
Sat 10 Jan 2015, 1:00pm-4:00pm
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Nicolaos Kapouleas
Brown University
Tue 13 Jan 2015, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
TBA
ESB 2012
Tue 13 Jan 2015, 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


Note for Attendees

Coffee, tea and cookies served at 2:30pm in the PIMS Lounge, ESB 4133.
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UCLA
Thu 5 Mar 2015, 3:30pm
Number Theory Seminar
room MATH 126
TBA
room MATH 126
Thu 5 Mar 2015, 3:30pm-4:30pm

Abstract

 
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UCLA
Fri 6 Mar 2015, 3:00pm
Department Colloquium
MATX 1100
TBA
MATX 1100
Fri 6 Mar 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


Note for Attendees

Coffee, tea and cookies served at 2:30pm in the PIMS Lounge, ESB 4133.
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TBA
Fri 20 Mar 2015, 3:00pm
Department Colloquium
MATX 1100
Graduate Research Award Lecture
MATX 1100
Fri 20 Mar 2015, 3:00pm-4:00pm

Abstract


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Yakov Sinai
Princeton University
Fri 23 Oct 2015, 3:00pm SPECIAL
Department Colloquium / PIMS Seminars and PDF Colloquiums
ESB2012
TBA-PIMS/UBC Distinguished Colloquium
ESB2012
Fri 23 Oct 2015, 3:00pm-4:00pm
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