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 Events
Mon 2 Mar 2015, 1:00pm
Math Education Research Reading
MATX1118
Communities in university mathematics by Biza, Jaworski and Hemmi
MATX1118
Mon 2 Mar 2015, 1:00pm-2:00pm

Abstract

 
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UBC Mathematics
Mon 2 Mar 2015, 3:00pm
Institute of Applied Mathematics
LSK 460
Stochastic domain decomposition for parallel grid generation
LSK 460
Mon 2 Mar 2015, 3:00pm-4:00pm

Abstract

In this talk a method for the parallel generation of adaptive meshes using stochastic domain decomposition is presented. The method rests on numerically evaluating the stochastic representation of the exact solution of a linear elliptic or linear parabolic mesh generator for generating the mesh at the interfaces of the sub-domains. Unlike traditional domain decomposition, this method hence does not require iteration on the sub-domains or optimization of the transmission conditions to generate adaptive meshes over the entire domain. We show the generation of adaptive meshes for prescribed mesh density functions and study the scaling properties of the algorithm. A few physical examples for the parallel generation of adaptive meshes for Burgers equation and the shallow-water equations are presented. This is joint work with Ronald Haynes and Emily Walsh.
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UBC
Mon 2 Mar 2015, 3:10pm
CRG Geometry and Physics Seminar
ESB 4127
Dg-manifolds as derived manifolds
ESB 4127
Mon 2 Mar 2015, 3:10pm-4:10pm

Abstract

Given two smooth maps of manifolds f:M \to L and g:N \to L, if they are not transverse, the fibered product M \times_L N may not exist, or may not have the correct cohomological properties. In the world of derived manifolds, such a fibered product always exists as a smooth object, regardless of transversality. In this talk we will describe recent progress of ours with D. Roytenberg on giving an accessible geometric model for derived manifolds using differential graded manifolds.
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UBC
Mon 2 Mar 2015, 4:00pm
Discrete Math Seminar
ESB 4127
Spectrum in Simplicial Complexes
ESB 4127
Mon 2 Mar 2015, 4:00pm-5:00pm

Abstract

 

Ramanujan graphs are k-regular graphs admitting optimal connectivity properties (namely, optimal expanders). Infinite families of such graphs were first constructed by Lubotzky, Phillips and Sarnak in 1988 by relating the spectrum of a graph with certain representations of GL_2(Q_p). These ideas were generalized to simplical complexes by Lubotzky, Samuels and Vishne in 2005. 
We will present a further generalization, showing that there is a natural way to relate spectral properties of simplicial complexes with certain representations of groups acting on their universal covers. Several results of this connection will be discussed. In particular, we strengthen the spectral properties of the complexes constructed by L-S-V. (Roughly speaking, we show that the complexes constructed by L-S-V have "optimal spectrum in all dimensions".)
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Stanford University
Tue 3 Mar 2015, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
On the topology and index of minimal surfaces
ESB 2012
Tue 3 Mar 2015, 3:30pm-4:30pm

Abstract

We show that for an immersed two-sided minimal surface in R^3, there is a lower bound on the index depending on the genus and number of ends. Using this, we show the nonexistence of an embedded minimal surface in R^3 of index 2, as conjectured by Choe. Moreover, we show that the index of an immersed two-sided minimal surface with embedded ends is bounded from above and below by a linear function of the total curvature of the surface. (This is joint work with Otis Chodosh)

 
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Bilkent University and McMaster Univerisity
Wed 4 Mar 2015, 3:15pm
Topology and related seminars
ESB 4133
Finite group actions on homotopy spheres
ESB 4133
Wed 4 Mar 2015, 3:15pm-4:15pm

Abstract

We are interested in classifying all finite groups which can act  on a finite CW-complex homotopy equivalent to a sphere, such that all isotropy subgroups are rank one groups, i.e., they do not include Z/pxZ/p  for any prime p. The equivalent question for free actions (all isotropy subgroups are trivial) has been answered completely by the works of P.A. Smith and  R. Swan. For actions with rank one isotropy, we give a list of group theoretical conditions which guarantee the existence of such actions. Some of these conditions are necessary conditions depending on assumptions on fixed point subspaces. This is a joint work with Ian Hambleton.
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TBA
Thu 5 Mar 2015, 3:30pm
Number Theory Seminar
room MATH 126
room MATH 126
Thu 5 Mar 2015, 3:30pm-4:30pm

Abstract

 
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Mathematics, University of Bath
Fri 6 Mar 2015, 4:00pm SPECIAL
Institute of Applied Mathematics
Canfor Policy Rm 1600, SFU Harbour Centre, Downtown Vancouver
Data Assimilation and Adaptivity
Canfor Policy Rm 1600, SFU Harbour Centre, Downtown Vancouver
Fri 6 Mar 2015, 4:00pm-5:00pm

Abstract

Data assimilation is the process of systematically including (often noisy) data into a forecast. It is now widely used in numerical weather prediction and its positive impact on the accuracy of weather forecasts is unquestionable. Indeed improvements in our ability to forecast the weather over the last decade are a reflection on the increasing volume of data available, improved computational methods and (significantly) much improved algorithms for incorporating this data into the forecast. However, many problems remain, including dealing with the sheer volume of the data and the inherent complexity of the weather and climate, understanding the effects of data and model error, and of reducing spurious correlations between the data and the forecast.

In this talk I will give a survey of various techniques that are used operationally to implement data assimilation procedures in weather (and climate) forecasting including the Ensemble Kalman Filter, and the 4D-Var method.

I will discuss their various advantages and disadvantages, the nature of the errors and ways to minimise these. In particular I will show that the use of adaptive numerical methods can significantly improve the performance

of the 4D-Var method. Hopefully I will show that used carefully Data Assimilation techniques can significantly improve our ability to forecast the weather of Planet Earth.

Joint work with Mike Cullen and Chiara Piccolo at the Met Office.

Note for Attendees

Note SFU downtown venue. Reception at 3:30 pm (light refreshments).
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UBC
Mon 9 Mar 2015, 3:00am
CRG Geometry and Physics Seminar
ESB 4127
The Donaldson-Thomas theory of K3xE via motivic and toric methods
ESB 4127
Mon 9 Mar 2015, 3:00am-4:00pm

Abstract

 Donaldson-Thomas invariants are fundamental deformation invariants of Calabi-Yau threefolds. We describe a recent conjecture of Oberdieck and Pandharipande which predicts that the (three variable) generating function for the Donaldson-Thomas invariants of K3xE (the product of a K3 surface and an elliptic curve) is given by the reciprocal of the Igusa cusp form of weight 10. For each fixed K3 surface of genus g, the conjecture predicts that the corresponding (two variable) generating function is given by a particular meromorphic Jacobi form. We prove the conjecture for K3 surfaces of genus 0 and genus 1. Our computation uses a new technique which mixes motivic and toric methods.  
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Colorado State University
Tue 10 Mar 2015, 4:00pm
Discrete Math Seminar
TBA
TBA
TBA
Tue 10 Mar 2015, 4:00pm-5:00pm

Abstract


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University of Washington
Wed 11 Mar 2015, 3:10pm
Probability Seminar
ESB 2012
The frog model on trees
ESB 2012
Wed 11 Mar 2015, 3:10pm-4:00pm

Abstract

Fix a graph G and place some number (random or otherwise) of sleeping frogs at each site, as well as one awake frog at the root. Set things in motion by having awake frogs perform independent simple random walk, waking any "sleepers" they encounter. Say the model is recurrent if the root is a.s. visited by infinitely many frogs and otherwise transient. When G is the rooted d-ary tree with one-frog-per-site we prove a phase transition from recurrence to transience as d increases. Alternatively, for fixed d with Poi(m)-frogs-per-site we prove a phase transition from transience to recurrence as m increases. The proofs use two different recursions and two different versions of stochastic domination. Several open problems will be discussed. Joint with Christopher Hoffman and Tobias Johnson.
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Osaka University
Wed 11 Mar 2015, 3:15pm
Topology and related seminars
ESB 4133
Pseudo-Anosovs with small dilatations in the hyperelliptic handlebody groups and spherical Hilden groups
ESB 4133
Wed 11 Mar 2015, 3:15pm-4:15pm

Abstract

This is a joint work with Susumu Hirose. We consider pseudo-Anosov elements of the mapping class groups on orientable surfaces. We are interested in a numerical invariant of pseudo-Anosovs, called the dilatation. The logarithm of the dilatation of a pseudo-Anosov mapping class is called the entropy. If we fix a surface, then the set of dilatations of pseudo-Anosovs defined on the surface is closed and discrete. In particular we can talk about a minimum of any subset of dilatations defined on the surface in question. 

Penner proved that the minimal entropy of pseudo-Anosovs defined on a closed surface of genus g behaves like 1/g. Later Hironaka proved that the minimal entropy of pseudo-Anosovs in the handlebody subgroup on a closed surface of genus $g$ also behaves like 1/g. We prove that the the minimal entropy of the hyperelliptic handlebody sugbroup of genus g has the same asymptotic behavior. (Our examples of pseudo-Anosovs improve the upper bound of the minimal entropy of the handlebody sugbroup given by Hironaka.) To do this, we study the spherical Hilden subgroup of the mapping class group defined on a sphere with 2n punctures, and we construct a sequence of pseudo-Anosovs with small dilatations in the spherical Hilden subgroups.
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Colorado State University
Thu 12 Mar 2015, 3:30pm
Number Theory Seminar
room MATH 126
Local heuristics and exact formulas for elliptic curves over finite fields
room MATH 126
Thu 12 Mar 2015, 3:30pm-4:30pm

Abstract

An isogeny class of elliptic curves over a finite field is determined by a quadratic Weil polynomial. Gekeler has given a beautiful product formula, purely in terms of congruence considerations involving that polynomial, for the size of such an isogeny class; an equidistribution hypothesis too strong to be true apparently calculates this cardinality.
 
I will give a new, transparent explanation, worked out with Julia Gordon, for this phenomenon. It turns out that Gekeler's formula computes an adelic orbital integral which, thanks to work of Langlands and Kottwitz, visibly calculates the desired quantity.
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Brown University
Fri 13 Mar 2015, 3:00pm
Department Colloquium
ESB 2012 (PIMS)
The mathematics of lattice-based cryptography (PIMS-UBC Distinguished Colloquium)
ESB 2012 (PIMS)
Fri 13 Mar 2015, 3:00pm-4:00pm

Abstract


Note for Attendees

Coffee, tea and cookies served at 2:30pm in the PIMS Lounge, ESB 4133.
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Imperial College
Mon 16 Mar 2015, 3:10pm
CRG Geometry and Physics Seminar
ESB4127
Mirror Symmetry and the Classification of Fano Manifolds
ESB4127
Mon 16 Mar 2015, 3:10pm-4:10pm

Abstract

 
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UBC
Tue 17 Mar 2015, 2:00pm SPECIAL
Topology and related seminars
ESB 4133
ESB 4133
Tue 17 Mar 2015, 2:00pm-3:00pm
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Mario Garcia Armas
Mathematics, UBC
Thu 19 Mar 2015, 12:30pm SPECIAL
One Time Event
Room 203 of the Graduate Student Centre (6371 Crescent Rd.), UBC
Doctoral Exams
Room 203 of the Graduate Student Centre (6371 Crescent Rd.), UBC
Thu 19 Mar 2015, 12:30pm-2:30pm

Details


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TBA
Thu 19 Mar 2015, 3:30pm
Number Theory Seminar
room MATH 126
room MATH 126
Thu 19 Mar 2015, 3:30pm-4:30pm

Abstract

 
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Gangwei Wang
UBC and Beijing Institute of Technology
Thu 19 Mar 2015, 4:30pm
Symmetries and Differential Equations Seminar
Math 125
Symmetry analysis and conservation laws for fractional order partial differential equations Part II
Math 125
Thu 19 Mar 2015, 4:30pm-5:30pm

Abstract

In this second talk, we again consider symmetries and conservation laws of FPDEs equation with Riemann-Liouville derivatives. Within the framework of Lie group theory, we extend Lie group analysis to solve problems involving FPDEs. Finally, we give further examples to illustrate applications of the methods. Some open questions will be discussed.
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UBC
Fri 20 Mar 2015, 3:00pm
Department Colloquium
LSK 200 (Note the special location)
Graduate Research Award Lecture
LSK 200 (Note the special location)
Fri 20 Mar 2015, 3:00pm-4:00pm

Abstract


Note for Attendees

Refreshments will be served at 2:40pm in the Math Lounge area, MATH 125 before the colloquium.
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Ed Kroc
Mathematics, UBC
Fri 20 Mar 2015, 4:00pm SPECIAL
One Time Event
Room 203 of the Graduate Student Centre (6371 Crescent Rd), UBC
Doctoral Exams
Room 203 of the Graduate Student Centre (6371 Crescent Rd), UBC
Fri 20 Mar 2015, 4:00pm-6:00pm

Details


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Nishant Chandgotia
Mathematics, UBC
Tue 24 Mar 2015, 12:00pm SPECIAL
One Time Event
Room 126 of the Mathematics Bldg.
Doctoral Exams
Room 126 of the Mathematics Bldg.
Tue 24 Mar 2015, 12:00pm-2:00pm

Details

TBA
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Korea Institute for Advanced Study
Tue 24 Mar 2015, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
New characterizations of the catenoid and helicoid
ESB 2012
Tue 24 Mar 2015, 3:30pm-4:30pm

Abstract

Bernstein and Breiner found a characterization of the catenoid that the area of a minimal annulus in a slab is bigger than that of the maximally stable catenoid in the same slab. We give a simpler proof of their theorem and extend the theorem to some minimal surfaces with genus (joint work with Benoit Daniel). New characterizations of the helicoid recently proved by Eunjoo Lee will be also presented.
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UBC
Wed 25 Mar 2015, 3:15pm
Topology and related seminars
ESB 4133
ESB 4133
Wed 25 Mar 2015, 3:15pm-4:15pm
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Subhajit Jana
UBC
Thu 26 Mar 2015, 3:30pm
Number Theory Seminar
room MATH 126
TBA
room MATH 126
Thu 26 Mar 2015, 3:30pm-4:30pm

Abstract

 
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UBC
Fri 27 Mar 2015, 3:00pm
Department Colloquium
ESB 2012
CRM-Fields-PIMS prize lecture: algebraic stacks and the inertia operator
ESB 2012
Fri 27 Mar 2015, 3:00pm-4:00pm

Abstract

Motivated by subtle questions in Donaldson-Thomas theory, we study the spectrum of the inertia operator on the Grothendieck module of algebraic stacks. We hope to give an idea of what this statement means.  Along the way, we encounter some elementary, but apparently new, questions about finite groups and matrix groups.  Prerequisites for this talk: a little linear algebra, and a little group theory.

Note for Attendees


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Carmen Bruni
Mathematics, UBC
Mon 30 Mar 2015, 9:00am SPECIAL
One Time Event
Room 203 of the Graduate Student Centre (6371 Crescent Rd), UBC
Doctoral Exams
Room 203 of the Graduate Student Centre (6371 Crescent Rd), UBC
Mon 30 Mar 2015, 9:00am-11:00am

Details


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Mathematics Manchester
Mon 30 Mar 2015, 3:00pm SPECIAL
Institute of Applied Mathematics
LSK 460
Modelling plant cell and tissue growth
LSK 460
Mon 30 Mar 2015, 3:00pm-4:00pm

Abstract

 
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Felipe Garcia Ramos Aguilar
Mathematics, UBC
Tue 31 Mar 2015, 12:30pm SPECIAL
One Time Event
Room 203 of the Graduate Student Centre (6371 Crescent Road), UBC
Doctoral Exams
Room 203 of the Graduate Student Centre (6371 Crescent Road), UBC
Tue 31 Mar 2015, 12:30pm-2:30pm

Details


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TBA
Fri 10 Apr 2015, 3:00pm
Department Colloquium
LSK 200
LSK 200
Fri 10 Apr 2015, 3:00pm-4:00pm

Abstract


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UCLA
Thu 21 May 2015, 3:30pm
Number Theory Seminar
room MATH 126
TBA
room MATH 126
Thu 21 May 2015, 3:30pm-4:30pm

Abstract

 
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Fri 11 Sep 2015, 3:00pm
Department Colloquium
reserved
Fri 11 Sep 2015, 3:00pm-4:00pm

Abstract


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Yakov Sinai
Princeton University
Fri 23 Oct 2015, 3:00pm SPECIAL
Department Colloquium / PIMS Seminars and PDF Colloquiums
ESB2012
TBA-PIMS/UBC Distinguished Colloquium
ESB2012
Fri 23 Oct 2015, 3:00pm-4:00pm
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