UBC Math

Fri 30 Sep 2016, 3:00pm
Department Colloquium
ESB 2012

UBC Mathematics and PIMS Faculty Award Colloquium  On the local Langlands conjectures

ESB 2012
Fri 30 Sep 2016, 3:00pm4:00pm
Abstract
The Langlands program, initiated in the 1960s, is a set of conjectures predicting a unification of number theory and the representation theory of groups. More precisely, the Langlands correspondence provides a way to interpret results in number theory in terms of group theory, and vice versa.
In this talk we sketch a few aspects of the local Langlands correspondence using elementary examples. We then comment on some questions raised by the emerging "mod p" Langlands program.
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Department of Computer Science, UBC

Tue 4 Oct 2016, 12:30pm
Scientific Computation and Applied & Industrial Mathematics
ESB 4133 (PIMS Lounge)

Fast Iterative Solvers for CahnHilliard Problems

ESB 4133 (PIMS Lounge)
Tue 4 Oct 2016, 12:30pm1:30pm
Abstract
The CahnHilliard equation models the motion of interfaces between several phases. The underlying energy functional includes a potential for which different types were proposed in the literature. We consider smooth and nonsmooth potentials with a focus on the latter. In the nonsmooth case, we apply a function spacebased algorithm, which combines a MoreauYosida regularization technique with a semismooth Newton method. We apply classical finite element methods to discretize the problems in space. At the heart of our method lies the solution of large and sparse fully discrete systems of linear equations. Block preconditioners using effective Schur complement approximations are presented. For the smooth systems, we derive optimal preconditioners, which are proven to be robust with respect to crucial model parameters. Further, we prove that the use of the same preconditioners give poor approximations for the nonsmooth formulations. The preconditioners we present for the nonsmooth problems incorporate the regularization terms. Extensive numerical experiments show an outstanding behavior of our developed preconditioners. Our strategy applies to different CahnHilliard problems including phase separation and coarsening processes, image inpainting, and twophase flows.
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University of California at Irvine

Tue 4 Oct 2016, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012

On the first eigenvalue estimate for subLaplacian and Kohn Laplacian and Rigidity Theorems on pseudoHermitian CR manifolds

ESB 2012
Tue 4 Oct 2016, 3:30pm4:30pm
Abstract
In this talk, I will present a CRversion of LichnerowiczObata type theorem in a closed pseudoHermitian CR manifolds. It includes the lower bound estimates for the first positive eigenvalue for the both subLaplacian and Kohn Laplacian. I will also provide Obata type theorem associated to the subLaplacian and Kohn Laplacian on a closed pseudoHermitian manifold. As an application, we give some rigidity theorem when lower bound of eigenvalue is achieved. This is based on a joint work with X. Wang and a joint work with Duong N. Son and Wang. I will also talk about some ongoing work in this topic.
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UBC

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

Forbidden Berge hypergraphs

ESB 4127
Tue 4 Oct 2016, 4:00pm5:00pm
Abstract
Given two matrices A,B we say that A is a Berge hypergraph of B if there is a submatrix of B, say matrix D, and a row and column permutation of A, say matrix C, so that C<=D. Define Av(m,F) to be the set of all mrowed (0,1)matrices with no repeated columns and no Berge hypergraph F. Define Bh(m,F) to be the maximum, over all matrices A in Av(m,F), of the number of columns of A. We are interested in determining the asymptotic growth of Bh(m,F) for specific F. We show some techniques we can use to this end and mention the general results determined for F with 5 or fewer rows. We also show that if F is the vertexedge incidence matrix of a tree then bh(m,F) has a linear bound. When F is the vertexedge (s+t)x(st) incidence matrix of the bipartite graph K_{s,t} we show that finding Bh(m,F) relates to determining ex(m,K_r,K_{s,t} ), the maximum number of complete subgraphs K_r in a mvertex graph avoiding K_{s,t} as a subgraph. Recent papers by Alon and others have solved some cases.
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UBC

Wed 5 Oct 2016, 1:45pm
Mathematical Biology Seminar
PIMS (ESB 4th floor)

Hidden Patterns Revealed by Noise: semiarid vegetation patterns

PIMS (ESB 4th floor)
Wed 5 Oct 2016, 1:45pm2:45pm
Abstract
A deterministic model may sometimes seem to be a good description of the dynamics of an observed system but may have a longterm stable constant limit, whereas observations of the system itself show a noisy pattern. An example is semiarid vegetation patterns. Adding noise to the model may well reveal the pattern. In this talk I show some photos, talk about some math, and show some simulations. This is not a magic show.
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UBC Computer Science and PIMS

Wed 5 Oct 2016, 3:00pm
Probability Seminar
ESB 2012

On longest paths and diameter in random Apollonian networks

ESB 2012
Wed 5 Oct 2016, 3:00pm4:00pm
Abstract
Consider the following iterative construction of a random planar triangulation. Start with a triangle embedded in the plane. In each step, choose a bounded face uniformly at random, add a vertex inside that face and join it to the vertices of the face. After n – 3 steps, we obtain a random triangulated plane graph with n vertices, which is called a Random Apollonian Network (RAN). See http://www.math.cmu.edu/~ctsourak/ran.html for an example.
We prove that the diameter of a RAN is asymptotic to c log(n) in probability, where c ≈ 1.668 is the solution of an explicit equation. The proof adapts a technique of Broutin and Devroye for estimating the height of random trees.
We also prove that there exists a fixed s<1, such that eventually every selfavoiding walk in this graph has length less than n^s, which verifies a conjecture of Cooper and Frieze. Using a similar technique, we show that if r < d are fixed constants, then every rary subtree of a random dary recursive tree on n vertices has less than n^b vertices, for some b=b(d,r)<1.
Based on joint work with A. Collevecchio, E. Ebrahimzadeh, L. Farczadi, P. Gao, C. Sato, N. Wormald, and J. Zung.
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Western Washington University

Wed 5 Oct 2016, 3:00pm
Harmonic Analysis Seminar
MATH 126

On probabilistic Strichartz estimates for the NLS

MATH 126
Wed 5 Oct 2016, 3:00pm4:00pm
Abstract
We will begin by briefly discussing the nonlinear Schroedinger (NLS) equation and the corresponding classical Strichartz estimates. We will then introduce a socalled Wiener randomization of initial data and indicate how it leads to an improvement of the classical Strichartz estimates. As a toy application, we will show how, in contrast with the deterministic case, the energycritical cubic NLS in four dimensions is almost surely wellposed with respect to randomized initial data below the energy space. This is a joint work with Tadahiro Oh (University of Edinburgh) and Oana Pocovnicu (HeriotWatt University).
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University of Southern California

Wed 5 Oct 2016, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)

A new proof of the decomposition theorem

ESB 4133 (PIMS Lounge)
Wed 5 Oct 2016, 3:15pm4:15pm
Abstract
In this talk, we will discuss a new proof of the decomposition theorem of Beilinson, Bernstein, Deligne and Gabber for semisimple perverse sheaves of geometric origin on complex algebraic varieties. This proof follows from rather formal considerations of higher algebra, stable motivic homotopy theory and Grothendieck's six functors, avoiding both the positivecharacteristic methods of the original proof, and the delicate analysis of degenerations of mixed Hodge structures involved in M. Saito's proof.
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Harvard University, ENS

Fri 7 Oct 2016, 3:00pm
SPECIAL
Department Colloquium
ESB 2012

PIMSUBC Distinguished ColloquiumPropagation of chaos and irreversibility in gas dynamics

ESB 2012
Fri 7 Oct 2016, 3:00pm4:00pm
Abstract
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UBC

Tue 11 Oct 2016, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012

TBA

ESB 2012
Tue 11 Oct 2016, 3:30pm4:30pm
Abstract
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UBC Math

Wed 12 Oct 2016, 3:00pm
Probability Seminar
ESB 2012

TBA

ESB 2012
Wed 12 Oct 2016, 3:00pm4:00pm
Abstract
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UBC

Wed 12 Oct 2016, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)

TBA, part I

ESB 4133 (PIMS Lounge)
Wed 12 Oct 2016, 3:15pm4:15pm
Abstract
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TAMU

Thu 13 Oct 2016, 4:00pm
Discrete Math Seminar
Math 126


Math 126
Thu 13 Oct 2016, 4:00pm5:00am
Abstract
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UBC Math

Fri 14 Oct 2016, 3:00pm
Department Colloquium
Math Annex 1100

TBA

Math Annex 1100
Fri 14 Oct 2016, 3:00pm4:00pm
Abstract
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UBC

Mon 17 Oct 2016, 3:00pm
Harmonic Analysis Seminar
MATH 126

Large Sets Avoiding Patterns

MATH 126
Mon 17 Oct 2016, 3:00pm4:00pm
Abstract
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UBC

Tue 18 Oct 2016, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012

TBA

ESB 2012
Tue 18 Oct 2016, 3:30pm4:30am
Abstract
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Pomona College

Tue 18 Oct 2016, 4:00pm
Discrete Math Seminar
ESB 4127


ESB 4127
Tue 18 Oct 2016, 4:00pm5:00pm
Abstract
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University of Washington

Wed 19 Oct 2016, 3:00pm
Probability Seminar
ESB 2012

Extremal conformal metrics, spectral geometry, and distributional limits of graphs

ESB 2012
Wed 19 Oct 2016, 3:00pm4:00pm
Abstract
I will talk about an intrinsic approach to uniformization of a graph's geometry based on extremal discrete metrics. This method allows one to generalize known results about planar graphs that rely heavily on the theory of circle packings, and to obtain new information even for wellstudied models of planar graphs like the uniform infinite triangulation (UIPT) and quadrangulation (UIPQ).
It yields a short proof of Benjamini and Schramm's result that a distributional limit of boundeddegree planar graphs is almost surely recurrent. The same argument resolves a 2001 conjecture of those authors since it works also for Hminorfree graphs (and, in fact, a substantial generalization known as region intersection graphs).
GurelGurevich and Nachmias recently solved a central open problem by showing that UIPT and UIPQ are almost surely recurrent. By combining extremal discrete metrics with methods from spectral geometry, I will present a new proof of this fact that also gives explicit control on divergence of the Green function. If g(x, T) denotes the number of returns to the root at time T, we show that almost surely (over the choice of the random rooted graph), g(x,T) grows asymptotically at least as fast as log log T. This is a consequence of a general result that holds for any distributional limit of Hminorfree graphs and provides lower bounds on return probabilities based on the tails of the degree distribution of the root.
Finally, I will discuss extensions to general graphs and, in particular, give a characterization of the almost sure spectral dimension of a distributional limit in terms of the "conformal growth rate" of any sequence that approaches the limit graph. This has consequences for graphs that can be spherepacked in R^d for d > 2.
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UBC

Wed 19 Oct 2016, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)

TBA, part II

ESB 4133 (PIMS Lounge)
Wed 19 Oct 2016, 3:15pm4:15pm
Abstract
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UBC Math

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

TBA

Math Annex 1100
Fri 21 Oct 2016, 3:00pm4:00pm
Abstract
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UBC

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


Math 126
Mon 24 Oct 2016, 3:00pm4:00pm
Abstract
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UBC

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


ESB 4127
Tue 25 Oct 2016, 4:00pm5:00pm
Abstract
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Wed 26 Oct 2016, 3:00pm
Probability Seminar
ESB 2012

TBA

ESB 2012
Wed 26 Oct 2016, 3:00pm4:00pm
Abstract
TBA
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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)

TBA

ESB 4133 (PIMS Lounge)
Wed 26 Oct 2016, 3:15pm10:00am
Abstract
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McGill University

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

CRMFieldsPIMS Award Lecture: TBA

ESB 2012
Fri 28 Oct 2016, 3:00pm4:00pm
Abstract
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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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University of Oregon

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


ESB 2012
Tue 1 Nov 2016, 3:30pm4:30pm
Abstract
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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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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

TBA

ESB 2012
Wed 9 Nov 2016, 3:00pm4:00pm
Abstract
TBA
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University of Washington

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

TBA

ESB 4133 (PIMS Lounge)
Wed 9 Nov 2016, 3:15pm10:00am
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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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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Reed College

Wed 16 Nov 2016, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)

TBA

ESB 4133 (PIMS Lounge)
Wed 16 Nov 2016, 3:15pm10:00am
Abstract
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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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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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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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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 (A light reception) are served in ESB 4133 from 2:30pm3:00pm before the colloquium.