Mathematics Dept.
  Events
BC Safety Authority
Wed 1 Feb 2017, 3:00pm
Institute of Applied Mathematics / PIMS Seminars and PDF Colloquiums / Mathematics of Information and Applications Seminar
ESB 5104
A risk-based platform for accident prevention strategies
ESB 5104
Wed 1 Feb 2017, 3:00pm-4:00pm

Abstract

BC Safety Authority’s accident prevention strategy follows a risk based platform, called “bow tie” for ongoing management and prevention of major incidents. The bow tie method draws on the direct experience of safety management team and the data collected from various safety oversight programs in order to identify hazards and to properly incorporate critical controls into management systems. In addition, it raises awareness and improves understanding and risk knowledge of the potential major incidents and the reliance on critical controls that prevent those accidents from occurring.  Opportunities exist for greater connectivity among various databases to maximize the risk knowledge, especially the pre incident data based on inspections and post incident data.

Note: this event is the inaugural Vancouver Data Science Colloquium, co-sponsored by 
CANSSI, the Data Sciences Institute (DSI), the Institute for Applied Mathematics (IAM) and PIMS.
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University of Oregon
Wed 1 Feb 2017, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)
The mod-two cohomology of symmetric and alternating groups.
ESB 4133 (PIMS Lounge)
Wed 1 Feb 2017, 3:15pm-4:15pm

Abstract

We present mod-two cohomology of both symmetric and alternating groups as (almost) Hopf rings. 

As is being seen in subjects such as representation stability, in these settings one gains substantial insight by considering all cases together, binding them with some structure.  For these group cohomologies, that structure is a transfer or induction product, akin to taking external tensor product of S_n and S_m representations and inducing up to S_{n+m}.  This product along with cup product and a standard coproduct together define a ring object in the category of coalgebras in the setting of symmetric groups, and are close enough to such an object for practical purposes in the setting of symmetric groups. 

Settings such as general linear groups over finite fields now beg for investigation, as do a number of questions internal to topology (e.g. Margolis homology, working towards Morava K-theory) and at the interface with algebra (e.g. how do analogous structures interface with current understanding of modular representation theory of symmetric groups).

We will aim for the talk to be accessible to algebraists.  While topology will be mentioned throughout, it will be presented in a supporting role, familiar to topologists but treatable as a black box when necessary to algebraists.
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Aaron Zeff Palmer
Cornell University
Wed 1 Feb 2017, 4:00pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012 (Note the unusual time: 4-5 pm on Wednesday, Feb 1. )
Incompressibility and Global Injectivity in Second-Gradient Non-Linear Elasticity
ESB 2012 (Note the unusual time: 4-5 pm on Wednesday, Feb 1. )
Wed 1 Feb 2017, 4:00pm-5:00pm

Abstract

This talk addresses how the calculus-of-variations is applied to non-linear elasticity.  In physically realistic classical models, energy-minimizing deformations may not be smooth enough to satisfy the variational Euler-Lagrange equations.  However, with a second-gradient model we guarantee sufficient regularity to rigorously prove energy-minimizers satisfy such an equation and maintain incompressibility and/or global injectivity. 

The constraints of incompressibility and self-contact introduce subtle challenges of infinite-dimensional non-linear analysis. I will discuss the techniques and assumptions that we use to prove the existence of a distributional pressure for the incompressibility constraint and a measure-valued surface traction for the self-contact constraint.  This work was part of my dissertation research done under the supervision of Professor Timothy J. Healey at Cornell University.

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University of Munich
Thu 2 Feb 2017, 3:30pm SPECIAL
Diff. Geom, Math. Phys., PDE Seminar
MATH 102 (note special day/room)
The adiabatic theorem for quantum spin systems
MATH 102 (note special day/room)
Thu 2 Feb 2017, 3:30pm-4:30pm

Abstract

I will present an adiabatic theorem for the driven dynamics of ground state projections of a smooth family of many-body gapped quantum systems. The diabatic error is uniformly bounded in the volume of the interacting system. As an corollary, Kubo’s formula of linear response theory can be obtained in the thermodynamic limit.
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University of Munich
Fri 3 Feb 2017, 3:00pm
Department Colloquium
ESB 2012
What are ground state phases of matter?
ESB 2012
Fri 3 Feb 2017, 3:00pm-4:00pm

Abstract

While thermal phases of matter (liquid water vs solid ice) are mathematically well understood, the theoretical understanding of ground state phases (at zero temperature) is incomplete. The discoveries of last year’s physics Nobel laureates provide a framework valid for noninteracting systems with topological properties, and I shall discuss current efforts to extend some of it to phases of strongly interacting matter.

Note for Attendees

Tea and cookies will be served at 2:45 pm in the PIMS Lounge (ESB 4133) before this colloquium.
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Technion
Mon 6 Feb 2017, 3:00pm SPECIAL
Institute of Applied Mathematics
ESB 2012
Operator Representations for Geometry Processing
ESB 2012
Mon 6 Feb 2017, 3:00pm-4:00pm

Abstract

 

Note for Attendees

Reception preceding the talk in ESB 4133 (PIMS lounge). This is part of the IAM/PIMS distinguished colloquium series. 
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Stanford University
Mon 6 Feb 2017, 3:00pm
Algebraic Geometry Seminar
MATX 1102
Noether-Lefschetz Theory and Elliptic CY3's
MATX 1102
Mon 6 Feb 2017, 3:00pm-4:00pm

Abstract

The Hodge theory of surfaces provides a link between enumerative geometry and modular forms, via the cohomological theta correspondence.  I will present an approach to studying the Gromov-Witten invariants of Weierstrass fibrations over P^2, proving part of a conjectural formula coming from topological string theory.
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Chen Greif
Department of Computer Science, UBC
Tue 7 Feb 2017, 12:30pm
Scientific Computation and Applied & Industrial Mathematics
ESB 4133 (PIMS Lounge)
SPMR: a Family of Saddle-Point Minimum Residual Solvers
ESB 4133 (PIMS Lounge)
Tue 7 Feb 2017, 12:30pm-1:30pm

Abstract

We introduce SPMR, a new family of methods for iteratively solving saddle-point systems using a minimum or quasi-minimum residual approach. No symmetry assumptions are made. The basic mechanism underlying the method is a novel simultaneous bidiagonalization procedure that yields a simplified saddle-point matrix on a projected Krylov-like subspace, and allows for a monotonic short-recurrence iterative scheme. We develop a few variants, demonstrate the advantages of our approach, derive optimality conditions, and discuss connections to existing methods. Numerical experiments illustrate the merits of this new family of methods.

This is joint work with Ron Estrin.
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Foster Tom
UBC
Tue 7 Feb 2017, 4:00pm
Discrete Math Seminar
ESB 4127
Schur-Positivity of Equitable Ribbons, Part 2
ESB 4127
Tue 7 Feb 2017, 4:00pm-5:00pm

Abstract

Schur functions form an important basis for the space of symmetric functions and show up in areas from representation theory to quantum mechanics. We continue to investigate the problem of which ribbon Schur functions are most Schur-positive; that is, when the difference of two ribbon Schur functions is a nonnegative linear combination of Schur functions. In particular, we describe techniques leading to a powerful necessary condition and time permitting, lay out how to continue these methods in resolving long-standing conjectures.
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UBC
Wed 8 Feb 2017, 3:00pm
Probability Seminar
ESB 2012
Thresholds for contagious sets in random graphs
ESB 2012
Wed 8 Feb 2017, 3:00pm-4:00pm

Abstract

Bootstrap percolation with threshold r on a graph G evolves as follows: initially some of its vertices are infected, and then any vertex with at least r infected neighbors becomes infected. On the Erdos–Renyi graph G(n,p) we identify the sharp threshold for p, above which there is with high probability a set of size r whose infection results in the infection of the entire graph.
Joint work with Omer Angel.
 
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UBC
Thu 9 Feb 2017, 3:30pm
Number Theory Seminar
ESB 4127
Representations of reductive groups over local fields; Endoscopic classification of essentially tame supercuspidal representations for quasi-split classical groups
ESB 4127
Thu 9 Feb 2017, 3:30pm-5:15pm

Abstract

Part I: Representations of reductive groups over local fields

In this talk, we describe the representations of certain reductive groups over local fields and the representations of Weil groups. Then we review the class field theory for local fields and the Langlands correspondence for these reductive groups. The talk will be a brief overview of the representation theory of reductive groups over local fields, largely based on examples of low-rank groups.


Part II: Endoscopic classification of essentially tame supercuspidal representations for quasi-split classical groups

Continue from the last talk, we specify our reductive group \mathbf{G} to be a quasi-split classical group (special orthogonal, symplectic, unitary) over a p-adic field of odd residual characteristic. We describe the endoscopic classification, proved by Arthur and Mok, of certain supercuspidal representations and their L-packets of \mathbf{G}, under some regularity and tameness conditions. These representations can be described by inducing types constructed by Bushnell-Kutzko, Stevens, or Yu, and they correspond to Langlands parameters related to characters of elliptic maximal tori of \mathbf{G}.
(This work is partly joint with Corinne Blondel.)
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I-Kun Chen
Kyoto University
Tue 14 Feb 2017, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
Singularity and regularity for the stationary solutions to linearized Boltzmann equations
ESB 2012
Tue 14 Feb 2017, 3:30pm-4:30pm

Abstract

In Boltzmann equation, the interplay among free transport, collision, and boundary yields rich phenomena in regularity of solutions. In this talk, we will first introduce the logarithmic singularity both on macroscopic and microscopic variables due to the boundary. Then, we will discuss the regularity of stationary solutions in a convex domain. Finally, we will provide the analysis that realizes our observation.

Coffee and cookie will be provided before the seminar at the PIMS lounge.

Prof. I-Kun Chen is currently a Senior Lecturer at the Department of Applied Analysis and Complex Dynamical Systems, Kyoto University, http://www.acs.i.kyoto-u.ac.jp/en.html . He is visiting UBC between Feb 8-22, 2017.
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Kyoto University
Wed 15 Feb 2017, 3:00pm
Probability Seminar
ESB 2012
Completely Symmetric Resistance Forms on the Stretched Sierpinski Gasket
ESB 2012
Wed 15 Feb 2017, 3:00pm-4:00pm

Abstract

 The stretched Sierpinski gasket, SSG for short, is the space obtained by replacing every branching point of the Sierpinski gasket by an interval. It has also been called ``deformed Sierpinski gasket'' or ``Hanoi attractor''. As a result, it is the closure of a countable union of intervals and one might expect that a diffusion on SSG is essentially a kind of gluing of the Brownian motions on the intervals. In fact, there have been several works in this direction. There still remains, however, ``reminiscence'' of the Sierpinski gasket in the geometric structure of SSG and the same should therefore be expected for diffusions. This paper shows that this is the case. In this work, we identify all the completely symmetric resistance forms on SSG. A completely symmetric resistance form is a resistance form whose restriction to every contractive copy of SSG in itself is invariant under all geometrical symmetries of the copy, which constitute the symmetry group of the triangle.  We prove that completely symmetric resistance forms on SSG can be sums of the Dirichlet integrals on the intervals with some particular weights, or a linear combination of a resistance form of the former kind and the standard resistance form on the Sierpinski gasket.
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North Carolina State University
Wed 15 Feb 2017, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)
Representation stability in configuration spaces via Whitney homology of the partition lattice
ESB 4133 (PIMS Lounge)
Wed 15 Feb 2017, 3:15pm-4:15pm

Abstract

In recent years, important families of symmetric group representations have come to be better understood through the perspective of representation stability, a viewpoint introduced and developed by Thomas Church, Jordan Ellenberg, and Benson Farb, among others. A fundamental example of representation stability is the S_n-module structure for the $i$-th cohomology of the configuration space of n distinct, labeled points in the plane, or more generally in a connected, orientable manifold, as $i$ is held fixed and n grows.  For the plane, this translates to Whitney homology of the partition lattice via an S_n-equivariant version of the Goresky-MacPherson formula. This talk will survey the combinatorial literature regarding the partition lattice and discuss what new things this can tell us about representation stability for configuration spaces.  In particular, we deduce new, sharp stability bounds and representation theoretic structure through a combination of symmetric function technology and poset topology.  This is a joint work with Vic Reiner.
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Technion
Thu 16 Feb 2017, 3:30pm
Number Theory Seminar
ESB 4127
Homogeneous dynamics and number theory
ESB 4127
Thu 16 Feb 2017, 3:30pm-5:15pm

Abstract

I will discuss some aspects of the tight connection between the study of certain dynamical systems and number theory (most notably to questions in Diophantine approximation and the geometry of numbers).
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UCSD
Mon 20 Feb 2017, 3:00pm SPECIAL
Number Theory Seminar / PIMS Seminars and PDF Colloquiums
ESB 4127
Representations in Arithmetic: Adic spaces (Lecture 1)
ESB 4127
Mon 20 Feb 2017, 3:00pm-4:00pm

Abstract

This event is part of the PIMS Focus Group on Representations in Arithmetic - see the PIMS page for the talk.

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UCSD
Tue 21 Feb 2017, 3:00pm SPECIAL
Number Theory Seminar / PIMS Seminars and PDF Colloquiums
ESB 4127
Representations in Arithmetic: Adic spaces (Lecture 2)
ESB 4127
Tue 21 Feb 2017, 3:00pm-4:00pm

Abstract

This event is part of the PIMS Focus Group on Representations in Arithmetic - see the PIMS page for the talk.

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UCSD
Tue 28 Feb 2017, 10:00am SPECIAL
Number Theory Seminar / PIMS Seminars and PDF Colloquiums
ESB 4127
Representations in Arithmetic: Adic spaces (Lecture 3)
ESB 4127
Tue 28 Feb 2017, 10:00am-11:00am

Abstract

This event is part of the PIMS Focus Group on Representations in Arithmetic - see the PIMS page for the talk.

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UBC Math
Tue 28 Feb 2017, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
Optimal Mass transport as a natural extension of classical mechanics to the manifold of probability measures
ESB 2012
Tue 28 Feb 2017, 3:30pm-4:30pm

Abstract

I will describe how deterministic and stochastic dynamic optimal mass transports are to Mean Field Games what the classical calculus of variations offers to classical mechanics.
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UCSD
Tue 28 Feb 2017, 3:30pm SPECIAL
Number Theory Seminar
ESB 4127
The unreasonable effectiveness of p-adic Hodge theory
ESB 4127
Tue 28 Feb 2017, 3:30pm-4:30pm

Abstract

As its name is meant to suggest, the subject of p-adic Hodge theory was historically concerned with the relationship between different cohomology theories attached to p-adic algebraic varieties. Within p-adic Hodge theory, the concept of a perfectoid space (discussed in my PIMS lectures) arose quite naturally and has led to improvements in the subject which were in some sense "expected".

However, it also had several "unexpected" applications rather far afield. We'll survey three of these: Deligne's weight-monodromy conjecture (Scholze); Galois representations associated to torsion cohomology of arithmetic groups (Scholze, Caraiani-Scholze); and the direct summand conjecture of commutative algebra (Andre, Bhatt).
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