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

Fri 28 Oct 2016, 11:10am
SPECIAL
Topology and related seminars
ESB 4133 (PIMS Lounge)

Nonpositive Immersions and Counting Cycles

ESB 4133 (PIMS Lounge)
Fri 28 Oct 2016, 11:10am12:10pm
Abstract
The "nonpositive immersion" property is a condition on a 2complex X that generalizes being a surface. When X has this property, its fundamental group appears to have has some very nice properties which I will discuss. I will spend the remainder of the talk outlining a proof that the nonpositive immersion property holds for a 2complex obtained by attaching a single 2cell to a graph. This was proven recently with Joseph Helfer and also independently by Lars Louder and Henry Wilton.
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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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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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Yale University

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

The torsion order of an algebraic variety

MATH 126
Mon 31 Oct 2016, 3:00pm4:00pm
Abstract
The minimal multiple of the diagonal to admit a decomposition in the sense of Bloch and Srinivas is called the torsion order of a smooth projective variety. It is bounded above by the greatest common divisor of the degrees of all unirational parameterizations, and is a stable birational invariant. Recently, a degeneration method initiated by Voisin, and developed by ColliotThélène and Pirutka, has led to a breakthrough in establishing lower bounds for the torsion order, hence obstructions to stable rationality. The power of this method lies in its mix of inputs from algebraic cycles, Hodge theory, algebraic Ktheory, birational geometry, and singularity theory. I will survey the state of the art of this theory, which includes recent work of Chatzistamatiou and Levine, as well as provide some new examples.
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Sloan School of Management, MIT

Tue 1 Nov 2016, 12:30pm
Scientific Computation and Applied & Industrial Mathematics
ESB 4133 (PIMS Lounge)

Mixedinteger convex optimization

ESB 4133 (PIMS Lounge)
Tue 1 Nov 2016, 12:30pm1:30pm
Abstract
Mixedinteger convex optimization problems are convex problems with the additional (nonconvex) constraints that some variables may take only integer values. Despite the past decades' advances in algorithms and technology for both mixedinteger *linear* and *continuous, convex* optimization, mixedinteger convex optimization problems have remained relatively more challenging and less widely used in practice. In this talk, we describe our recent algorithmic work on mixedinteger convex optimization which has yielded advances over the state of the art, including the globally optimal solution of open benchmark problems. Based on our developments, we have released Pajarito, an opensource solver written in Julia and accessible from popular optimization modeling frameworks. Pajarito is immediately useful for solving challenging mixed combinatorial continuous problems arising from engineering and statistical applications.
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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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Note for Attendees