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, 3:00pm4:00pm
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 diffusionreaction 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 superdiffusion singularity when it attains its {\it a priori} known upper bound. I will summarize some analytical (wellposedness) 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 clusterandchannel 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.
hide

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, 3:00pm4:00pm
Abstract
We are interested in the problem of solving a translationinvariant 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 HeathBrown 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.
hide

Kyoto University

Tue 4 Nov 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012

TBA

ESB 2012
Tue 4 Nov 2014, 3:30pm4:30pm
Abstract
hide

SFU

Tue 4 Nov 2014, 4:00pm
Discrete Math Seminar
ESB 4127

An infinite family of invWilfequivalent permutation pairs

ESB 4127
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.
hide

MIT

Wed 5 Nov 2014, 3:00pm
SPECIAL
Discrete Math Seminar / Harmonic Analysis Seminar
MATX1118

On geometric incidences

MATX1118
Wed 5 Nov 2014, 3:00pm4:00pm
Abstract
hide

York University

Wed 5 Nov 2014, 3:10pm
Probability Seminar
ESB 2012

Random walk in nonelliptic random environments

ESB 2012
Wed 5 Nov 2014, 3:10pm4:10pm
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 nonzero asymptotic speeds).
hide

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, 12:00pm1:00pm
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 settingswhere each column of the data matrix comes from a separate sensorthe 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 costeffective manner. Such systems typically involve collections of batteryoperated 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.
hide

UBC

Thu 6 Nov 2014, 12:30pm
Graduate Student Seminar
Math 225

Supersymmetric integration

Math 225
Thu 6 Nov 2014, 12:30pm1:45pm
Abstract
We begin by defining the Grassmann integral of a function of both commuting ("bosonic") and anticommuting ("fermionic") variables. An important example is the mixed bosonicfermionic ("supersymmetric") Gaussian integral, which exhibits a surprising selfnormalization property. Time permitting, we will mention applications of the Grassmann integral to the representation of selfavoiding walk as a supersymmetric quantum field theory.
hide


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, 12:30pm2:30pm
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 loglinear 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 pseudolikelihood estimators.
Finally, for linear and nonlinear 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.
hide

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, 3:30pm4:30pm
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 Ralgebras, quadratic spaces equipped with a group action ("Gforms"), and systems of quadratic forms. The results can be regarded as versions of the Grothendieck–Serre conjecture for certain nonreductive groups. (Joint work with Eva Bayer–Fluckiger.)
hide

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
hide

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, 3:00pm4:00pm
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 AdarrioBerry, Guillaume Chapuy, Luc Devroye, Gabor Lugosi, Neil Olver, Yuval Peres and Richard Balka.
hide

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, 3:00pm4:00pm
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.
hide

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, 3:00pm4:00pm
Abstract
TBA
hide

UBC

Wed 12 Nov 2014, 3:15pm
Topology and related seminars
ESB 4133

TBA

ESB 4133
Wed 12 Nov 2014, 3:15pm4:15pm
hide


Thu 13 Nov 2014, 12:00pm
One Time Event
4133 ESB (PIMS lounge)

TBA

4133 ESB (PIMS lounge)
Thu 13 Nov 2014, 12:00pm1:00pm
Details
hide

Morningside Center of Mathematics and Purdue

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

Introduction to Mochizuki's works on interuniversal Teichmuller theory

room MATH 126
Thu 13 Nov 2014, 3:30pm4:30pm
Abstract
Interuniversal 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 padic Teichmuller theory of Mochizuki. In this theory, the ring structure of a number field is subject to nonring theoretic deformation. Absolute anabelian geometry, a refinement of anabelian geometry, plays a crucial role in interuniversal Teichmuller theory. In this talk, we will try to give an introduction to these ideas.
hide

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, 3:00pm4:00pm
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).
hide

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
hide

UBC

Tue 18 Nov 2014, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012

TBA

ESB 2012
Tue 18 Nov 2014, 3:30pm4:30pm
Abstract
hide

UBC

Wed 19 Nov 2014, 3:15pm
Topology and related seminars
ESB 4133

TBA

ESB 4133
Wed 19 Nov 2014, 3:15pm4:15pm
Abstract
hide


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


room MATH 126
Thu 20 Nov 2014, 3:30pm4:30pm
Abstract
hide

The University of Auckland

Fri 21 Nov 2014, 3:00pm
Department Colloquium
Math Annex 1100

Reducing lectures, making students responsible, and offering semiauthentic mathematical experiences.

Math Annex 1100
Fri 21 Nov 2014, 3:00pm4:00pm
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 semiauthentic mathematical experiences in which students work in small groups for up to two hours at a time guided by a lecturer on openended 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.
hide

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, 3:00pm4:00pm
Abstract
TBA
hide

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, 3:30pm4:30pm
Abstract
We prove the existence of a sequence of nondegenerate, in the sense of DuyckaertsKenigMerle, nodal nonradial solutions to the critical Yamabe problem or stationary energycritical wave equation.
hide


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, 4:00pm6:30pm
hide

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, 3:00pm4:00pm
Abstract
TBA
hide

MIT

Wed 26 Nov 2014, 3:15pm
Topology and related seminars
ESB 4133


ESB 4133
Wed 26 Nov 2014, 3:15pm4:15pm
hide

Oxford University

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

TBA

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


Fri 28 Nov 2014, 3:00pm
Department Colloquium
MATX 1100

Graduate Research Award lecture

MATX 1100
Fri 28 Nov 2014, 3:00pm4:00pm
Abstract
hide

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, 3:00pm4:00pm
Abstract
TBA
hide


Sat 10 Jan 2015, 9:00am
SPECIAL
One Time Event
To Be Announced

Analysis  Qualifying Exams

To Be Announced
Sat 10 Jan 2015, 9:00am12:00pm
hide


Sat 10 Jan 2015, 1:00pm
SPECIAL
One Time Event
To Be Announced

Differential Equations  Qualifying Exams

To Be Announced
Sat 10 Jan 2015, 1:00pm4:00pm
hide


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, 1:00pm4:00pm
hide

Brown University

Tue 13 Jan 2015, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012

TBA

ESB 2012
Tue 13 Jan 2015, 3:30pm4:30pm
Abstract
hide

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
hide

UCLA

Thu 5 Mar 2015, 3:30pm
Number Theory Seminar
room MATH 126

TBA

room MATH 126
Thu 5 Mar 2015, 3:30pm4:30pm
Abstract
hide

UCLA

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

TBA

MATX 1100
Fri 6 Mar 2015, 3:00pm4:00pm
Abstract
hide

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
hide


Fri 20 Mar 2015, 3:00pm
Department Colloquium
MATX 1100

Graduate Research Award Lecture

MATX 1100
Fri 20 Mar 2015, 3:00pm4:00pm
Abstract
hide

Princeton University

Fri 23 Oct 2015, 3:00pm
SPECIAL
Department Colloquium / PIMS Seminars and PDF Colloquiums
ESB2012

TBAPIMS/UBC Distinguished Colloquium

ESB2012
Fri 23 Oct 2015, 3:00pm4:00pm
hide

Note for Attendees
Refreshments will be served at 2:45pm in the Math Lounge area, MATH 125 before the colloquium.