UBC Math

Fri 21 Oct 2016, 3:00pm
Department Colloquium
Math Annex 1100

Numerical modelling and high performance computing of particleladen flows

Math Annex 1100
Fri 21 Oct 2016, 3:00pm4:00pm
Abstract
Particleladen flows are ubiquitous in environmental, geophysical and engineering processes. The intricate dynamics of these twophase flows is governed by momentum transfer between the continuous fluid phase and the dispersed particulate phase. In this talk, I will suggest a multiscale modelling framework for particleladen flows and address mathematical and computational issues related to the numerical simulation of this type of flow. Based on various simulation results, I will present what can already be achieved with existing numerical models as well as the next stages in the development of faster and more accurate solution methods as e.g. fast NavierStokes solvers on cartesian grids, Adaptive Mesh Refinement or highly scalable numerical tools.
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UBC

Mon 24 Oct 2016, 3:00pm
Harmonic Analysis Seminar
Math 126

(p,q)strong unboundedness for the maximal directional Hilbert transform in dimension n

Math 126
Mon 24 Oct 2016, 3:00pm4:00pm
Abstract
In 2007 G.A.Karagulyan proved that the maximal directional Hilbert transform over a set U of directions in the plane cannot be extended to a (2,q)strongly bounded operator for any q in the range 1 ≤ q < +∞. In this talk, I will describe my proof of the generalization of this result and show that, for any 1 < p ≤ 2, any 1 ≤ q < +∞ and any dimension n ≥ 2, the maximal directional Hilbert transform over an infinite set of directions in IR^n, cannot be extended to a (p,q)strongly bounded operator.
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UBC

Mon 24 Oct 2016, 3:00pm
Algebraic Geometry Seminar
MATX 1102

Tstructures on coherent sheaves and categorical actions

MATX 1102
Mon 24 Oct 2016, 3:00pm4:00pm
Abstract
I will review the notion of a tstructure and discuss some recent uses of tstructures on categories of coherent sheaves in (geometric) representation theory. After reviewing some traditional methods to obtain tstructures I will present a new construction that uses categorical Lie actions. As an application one recovers the category of "exotic sheaves", used in a recent proof of Lusztig's conjectures on a canonical bases for the Grothendieck group of Springer fibers by Bezrukavnikov and Mirković. The new construction is purely geometric, instead of using deep results from modular representation theory. This is joint work with Sabin Cautis.
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Departments of Mathematics, Earth and Ocean Science, UBC

Tue 25 Oct 2016, 12:30pm
Scientific Computation and Applied & Industrial Mathematics
ESB 4133 (PIMS Lounge)

Mimetic Multiscale Methods and their application to Maxwell's equations

ESB 4133 (PIMS Lounge)
Tue 25 Oct 2016, 12:30pm1:30pm
Abstract
Solving Maxwell's equations for earth science applications requires the discretization of large domains with sufficiently small mesh to capture local conductivity variation. Multiscale methods are discretization techniques that allow to use a coarse mesh and still obtain accuracy that is obtained through finer meshes. However, when considering the multiscale solution of vector equations, basic operator properties are not conserved. In this talk we will show how to extend multiscale methods for vector quantities and demonstrate their use for Maxwell's equations.
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McGill University

Tue 25 Oct 2016, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB2012

Curvature flows and the isoperimetric problems in geometry

ESB2012
Tue 25 Oct 2016, 3:30pm4:30pm
Abstract
Abstract: We will discuss two types of curvature flows designed to prove isoperimetric type inequalities. The first one is a mean curvature type flow, it was introduced in a previous joint work with Junfang Li in space forms. In a recent joint paper with Junfang Li and MuTao Wang, we consider a similar normalized hypersurface flow in the more general ambient setting of warped product spaces with general base. Under a natural necessary condition, the flow preserves the volume of the bounded domain enclosed by a graphical hypersurface, and monotonically decreases the hypersurface area. Under another condition with is related to the notion of “photon sphere” in general relativity, we establish the regularity and convergence of the flow, thereby solve the isoperimetric problem in warped product spaces. In a similar spirit, I will discuss a inverse mean curvature type flow in hyperbolic space to deal with AlexandrovFenchel type isoperimetric inequalities.
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UBC

Tue 25 Oct 2016, 4:00pm
Discrete Math Seminar
ESB 4127

A Hard Problem in Lattice Theory

ESB 4127
Tue 25 Oct 2016, 4:00pm5:00pm
Abstract
Lattice theory is the study of an intriguing class of partially ordered sets known as lattices. Within this subject, there are many hard open problems. One such problem is to determine which countable lattices are sublattices of free lattices. In this talk, we will describe past progress on this problem and propose possible methods of attack using finite and finite width lattices. This research was done while I was a masters student at the University of Calgary.
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Université de Montréal

Wed 26 Oct 2016, 1:45pm
Mathematical Biology Seminar
PIMS (ESB 4th floor)

Feedback, delays and oscillations in blood cell production

PIMS (ESB 4th floor)
Wed 26 Oct 2016, 1:45pm2:45pm
Abstract
The production and control of blood cells is regulation by an intricate system of coupled mechanisms built around differentiation and proliferation of cells emerging from a common pool, with hormonal feedback at various stages of the maturation process. By developing physiologically correct models of this system, and its perturbation under pharmaceutical interventions, such as oncological treatments, we are lead to the investigation of nonlinear systems of delaydifferential equations, some with statedependent delays. I will review the evolution of models for erythropoiesis (red blood cell production), and present recent models for neutrophils (white blood cells), incorporating the pharmacokinetics and pharmacodynamics of an oncological drug, together with the main regulating hormone, GCSF, and platelets.
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UBC Math

Wed 26 Oct 2016, 3:00pm
Probability Seminar
ESB 2012

Models of Gradient Type with SubQuadratic Action

ESB 2012
Wed 26 Oct 2016, 3:00pm4:00pm
Abstract
We consider models of gradient type, which is the density of a collection of realvalued random variables \phi :=\{\phi_x: x \in \Lambda\} given by Z^{1}\exp({\sum\nolimits_{j \sim k}V(\phi_j\phi_k)}). We focus our study on the case that V(\nabla\phi) = [1+(\nabla\phi)^2]^\alpha with 0 < \alpha < 1/2, which is a nonconvex potential. We introduce an auxiliary field t_{jk} for each edge and represent the model as the marginal of a model with logcancave density. Based on this method, we prove that finite moments of the fields \left<[v \cdot \phi]^p \right> are bounded uniformly in the volume. This leads to the existence of infinite volume measures. Also, every ergodic infinite volume Gibbs measure with mean zero for the potential V above scales to a Gaussian free field.
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NTNU Norwegian University of Science and Technology

Wed 26 Oct 2016, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)

Freaks of algebra  a topologist's exhibition

ESB 4133 (PIMS Lounge)
Wed 26 Oct 2016, 3:15pm4:15pm
Abstract
For this survey talk I will bring a bestiary of algebraic structures that are often less well known than they deserve to be. As I will explain, these are all related to symmetries and topology, and they have interesting symmetries of their own. This observation leads to new homology computations, and those will be the results that I will present along the way. Part of this work is joint with N. Wahl.
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Université de Savoie, Chambéry

Thu 27 Oct 2016, 3:30pm
Number Theory Seminar
MATH 126

Wave front sets of distributions in nonarchimedean analysis

MATH 126
Thu 27 Oct 2016, 3:30pm5:15pm
Abstract
In 1969, Sato and Hörmander introduced the notion of wave front set of a distribution in the real context. This concept gives a better understanding of operations on distributions such as product or pullback and it plays an important role in the theory of partial differential equations. In 1981, Howe introduced a notion of wave front set for some Lie group representations and in 1985, Heifetz gave an analogous version in the padic context. In this talk, in the tadic context in characteristic zero, using CluckersLoeser motivic integration we will present analogous constructions of test functions, distributions and wave front sets. In particular, we will explain how definability can be used as a substitute for topological compactness of the sphere in the real and padic contexts to obtain finiteness. This a joint work with R. Cluckers, and F. Loeser.
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McGill University

Fri 28 Oct 2016, 3:00pm
Department Colloquium
ESB 2012

CRMFieldsPIMS Award Lecture: The Cubical Route to Understanding Groups

ESB 2012
Fri 28 Oct 2016, 3:00pm4:00pm
Abstract
Cube complexes have come to play an increasingly central role within geometric group theory, as their connection to rightangled Artin groups provides a powerful combinatorial bridge between geometry and algebra. This talk will introduce nonpositively curved cube complexes, and then describe the developments that have recently culminated in the resolution of the virtual Haken conjecture for 3manifolds, and simultaneously dramatically extended our understanding of many infinite groups.
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Yale University

Mon 31 Oct 2016, 3:00pm
Algebraic Geometry Seminar
MATH 126

TBA

MATH 126
Mon 31 Oct 2016, 3:00pm4:00pm
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UBC

Mon 31 Oct 2016, 3:00pm
Harmonic Analysis Seminar
Math 126

Linear and trilinear Kakeyatype estimates in R^4

Math 126
Mon 31 Oct 2016, 3:00pm4:00pm
Abstract
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University of Oregon

Tue 1 Nov 2016, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012

Minimal hypersurfaces with free boundary and positive scalar curvature

ESB 2012
Tue 1 Nov 2016, 3:30pm4:30pm
Abstract
There is a wellknown technique due to SchoenYau from the late 70s which uses (stable) minimal hypersurfaces to find topological implications of a (closed) manifold's ability to support positive scalar curvature metrics. In this talk, we describe a version of this technique for manifolds with boundary and discuss how it can be used to study bordisms of positive scalar curvature metrics.
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University of California, San Diego

Wed 2 Nov 2016, 3:00pm
Probability Seminar
ESB 2012

TBA

ESB 2012
Wed 2 Nov 2016, 3:00pm4:00pm
Abstract
TBA
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Princeton University

Fri 4 Nov 2016, 3:00pm
SPECIAL
Department Colloquium
ESB 2012

PIMSUBC Distinguished ColloquiumTBA

ESB 2012
Fri 4 Nov 2016, 3:00pm4:00pm
Abstract
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Waterloo

Mon 7 Nov 2016, 3:00pm
Algebraic Geometry Seminar
MATX 1102

TBA

MATX 1102
Mon 7 Nov 2016, 3:00pm4:00am
Abstract
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Stanford University

Tue 8 Nov 2016, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012


ESB 2012
Tue 8 Nov 2016, 3:30pm4:30pm
Abstract
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University of Bath

Wed 9 Nov 2016, 3:00pm
Probability Seminar
ESB 2012

Phase transition in a sequential assignment problem on graphs

ESB 2012
Wed 9 Nov 2016, 3:00pm4:00pm
Abstract
We study the following game on a finite graph $G = (V, E)$. At the start, each edge is assigned an integer $n_e \ge 0$, $n = \sum_{e \in E} n_e$. In
round $t$, $1 \le t \le n$, a uniformly random vertex $v \in V$ is chosen and one of the edges $f$ incident with $v$ is selected by the player. The value
assigned to $f$ is then decreased by $1$. The player wins, if the configuration $(0, \dots, 0)$ is reached; in other words, the edge values never go negative.
Our main result is that there is a phase transition: as $n \to \infty$, the probability that the player wins approaches a constant $c_G > 0$ when $(n_e/n :
e \in E)$ converges to a point in the interior of a certain convex set $\mathcal{R}_G$, and goes to $0$ exponentially when $(n_e/n : e \in E)$ is
bounded away from $\mathcal{R}_G$. We also obtain upper bounds in the nearcritical region, that is when $(n_e/n : e \in E)$ lies close to $\partial
\mathcal{R}_G$. We supply quantitative error bounds in our arguments.
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University of Washington

Wed 9 Nov 2016, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)

Iterated Thom Spectra with Examples

ESB 4133 (PIMS Lounge)
Wed 9 Nov 2016, 3:15pm10:00am
Abstract
Given a fiber sequence of nfold loop spaces X>Y>Z, and morphism of nfold loop spaces Y>Pic(R) for R an E_{n+1}ring spectrum, we describe a method of producing a new morphism of (n1)fold loop spaces Z>Pic(MX), where MX is the Thom spectrum associated to the composition X>Y>Pic(R). This new morphism has associated Thom spectrum MY, but constructed directly as an MXmodule. In particular this induces a relative Thom isomorphism for MY over MX: MY⊗_{MX} MY = MY⊗Z. We will see a rough description of this construction as well as many examples allowing us to find equivalent forms of relative smash products of spectra like MString, MSpin, HZ/2, X(n) and many others. We also describe a way to use this construction to identify certain obstructions to giving a complex orientation on an associative ring spectrum.
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Reed College

Thu 10 Nov 2016, 3:15pm
SPECIAL
Topology and related seminars
ESB 4133 (PIMS Lounge)

The transfer map of free loop spaces

ESB 4133 (PIMS Lounge)
Thu 10 Nov 2016, 3:15pm4:15pm
Abstract
Associated to a fibration E > B with homotopy finite fiber is a stable wrong way map LB > LE of free loop spaces coming from the transfer map in THH. This transfer is defined under the same hypotheses as the BeckerGottlieb transfer, but on different objects. I will use duality in bicategories to explain why the THH transfer contains the BeckerGottlieb transfer as a direct summand. The corresponding result for the Atheory transfer may then be deduced as a corollary. When the fibration is a smooth fiber bundle, the same methods give a three step description of the THH transfer in terms of explicit geometry over the free loop space. (Joint work with C. Malkiewich)
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UBC

Thu 10 Nov 2016, 3:30pm
Number Theory Seminar
MATH 126

TBA

MATH 126
Thu 10 Nov 2016, 3:30pm5:15pm
Abstract
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TU Darmstadt, Department of Mechanical Engineering

Mon 14 Nov 2016, 3:00pm
Institute of Applied Mathematics
ESB 2012

New conservation laws of Euler and NavierStokes equations. Subtitle: Generic and dimensionally reduced cases for plane, axisymmetric and helically symmetric flows

ESB 2012
Mon 14 Nov 2016, 3:00pm4:00pm
Abstract
It has long been known that 3D timedependent NavierStokes equations for incompressible fluids admit the classical conservation laws (CL) of mass, momentum, angular momentum and centreofmass theorem. For inviscid flows, i.e. Eulers equation, this is extended by the conservation of helicity and energy. Employing the “direct method” (DM) by Anco, Bluman (1997) it has been shown that this set of conservation laws is complete for primitive variables. The DM is a substantial generalization of Noethers theorem and does not rely on a variational principle, and, further, is directly applicable to any type of differential equation, even dissipative ones. With this an additional infinite set of CL for NavierStokes equations in vorticity formulation are derived. Various examples are shown.
Interesting enough, even more CLs exist for Euler and NavierStokes equations in spatially reduced coordinate systems such as for plane, axisymmetric and helically symmetric flows. E.g. an infinite set of CLs for the generalization of helicity has been derived, and, surprisingly, even new CL for plane flows haven been identified.
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UBC

Mon 14 Nov 2016, 3:00pm
Number Theory Seminar
ESB 4127

TBA

ESB 4127
Mon 14 Nov 2016, 3:00pm5:00am
Abstract
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Massachusetts Institute of Technology

Wed 16 Nov 2016, 3:00pm
Probability Seminar
ESB 2012

TBA

ESB 2012
Wed 16 Nov 2016, 3:00pm4:00pm
Abstract
TBA
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UIC

Fri 18 Nov 2016, 1:00pm
Discrete Math Seminar
MATX1102

New developments in hypergraph Ramsey theory

MATX1102
Fri 18 Nov 2016, 1:00pm2:00pm
Abstract
I will describe lower bounds (i.e. constructions) for several hypergraph Ramsey problems. These constructions settle old conjectures of ErdosHajnal on classical Ramsey numbers as well as more recent questions due to ConlonFoxLeeSudakov and others on generalized Ramsey numbers and the ErdosRogers problem. Most of this is joint work with Andrew Suk.
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Penn State

Fri 18 Nov 2016, 3:00pm
Department Colloquium
Math Annex 1100

TBA

Math Annex 1100
Fri 18 Nov 2016, 3:00pm4:00pm
Abstract
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Purdue University

Mon 21 Nov 2016, 1:45pm
Harmonic Analysis Seminar


Mon 21 Nov 2016, 1:45pm2:45pm
Abstract
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Johns Hopkins University

Mon 21 Nov 2016, 3:00pm
SPECIAL
Department Colloquium
Math Annex 1100

Quests for Golden numbers, old and new

Math Annex 1100
Mon 21 Nov 2016, 3:00pm4:00pm
Abstract
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MIT

Mon 21 Nov 2016, 3:00pm
Algebraic Geometry Seminar
MATX 1102

TBA

MATX 1102
Mon 21 Nov 2016, 3:00pm4:00pm
Abstract
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UBC Math

Wed 23 Nov 2016, 3:00pm
Probability Seminar
ESB 2012

TBA

ESB 2012
Wed 23 Nov 2016, 3:00pm4:00pm
Abstract
TBA
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UBC

Wed 23 Nov 2016, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)

TBA

ESB 4133 (PIMS Lounge)
Wed 23 Nov 2016, 3:15pm1:15am
Abstract
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Emory University

Fri 25 Nov 2016, 3:00pm
SPECIAL
Department Colloquium
ESB 2012

TBAPIMSUBC Distinguished Colloquium

ESB 2012
Fri 25 Nov 2016, 3:00pm4:00pm
Abstract
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Imperial College

Mon 28 Nov 2016, 3:00pm
SPECIAL
Institute of Applied Mathematics
ESB 2012

The "Hole Story" of a forgotten function, and how to use it

ESB 2012
Mon 28 Nov 2016, 3:00pm4:00pm
Abstract
Motivated by problems arising in the applied sciences, I will tell the story of what might reasonably be called a "forgotten function". It was discovered in the late 1800s, but has hardly ever been used in the physical sciences even though, as I will show, its applications in science and engineering turn out to be many and varied.
In particular, I will survey a new theoretical approach to solving problems in what mathematicians call "multiply connected" domains. These are ubiquitous in applications; whenever two or more objects or entities (airfoils, bacteria, vortices, inhomogeneities in an elastic medium, black holes!...) interact in some ambient medium the analysis may call for the methods I will discuss.
Some illustrative example problems from applications, especially in fluid dynamics, will be described and their solutions explicitly constructed. I will also describe freely available numerical codes that we have developed for the computation of this "forgotten function" in order to promote its use.
We hope to demonstrate that the new methods are sufficiently general that they provide broad scope for tackling a variety of problems.
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U. Georgia

Tue 29 Nov 2016, 4:00pm
Discrete Math Seminar
ESB 4127

TBA

ESB 4127
Tue 29 Nov 2016, 4:00pm5:00pm
Abstract
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UBC Math

Wed 30 Nov 2016, 3:00pm
Probability Seminar
ESB 2012

TBA

ESB 2012
Wed 30 Nov 2016, 3:00pm4:00pm
Abstract
TBA
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University of California, San Diego

Fri 3 Mar 2017, 3:00pm
SPECIAL
Department Colloquium
ESB2012

PIMSUBC Distinguished ColloquiumTBA

ESB2012
Fri 3 Mar 2017, 3:00pm4:00pm
Abstract
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University of Grenoble

Fri 10 Mar 2017, 3:00pm
SPECIAL
Department Colloquium
ESB 2012

PIMSUBC Distinguished ColloquiumTBA

ESB 2012
Fri 10 Mar 2017, 3:00pm4:00pm
Abstract
PIMSUBC Distinguished Colloquium TBA
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University of Grenoble

Mon 13 Mar 2017, 3:00pm
Algebraic Geometry Seminar
MATH 126

TBA

MATH 126
Mon 13 Mar 2017, 3:00pm4:00pm
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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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Note for Attendees
Refreshments will be served in MATH 125 at 2:45pm before the colloquium.