Mathematics

Asymmetric Ramsey properties of random graphs for cliques and cycles

Speaker: 
Leticia Mattos, IMPA
Date: 
Thu, Dec 3, 2020
Location: 
PIMS, University of Victoria
Zoom
Abstract: 

See attached PDF

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Uniqueness of Clusters in Percolation

Speaker: 
Nishant Chandgotia
Date: 
Mon, Dec 7, 2020
Location: 
University of Utah
Zoom
Abstract: 

Suppose mu is a probability measure which is shift invariant on {0,1}^{Z^d} and we know that for almost every configuration x in {0,1}^{Z^d} there are connected components of 1s which are infinite. In this talk, we will follow a paper by Burton and Keane (generalising results by Aizenman, Kesten and Newman) to give an elegant proof of the fact that, under fairly general conditions (say full support), the number of connected components of infinite cardinality is at exactly one.

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Adjusted Visibility Metric for Scientific Articles

Speaker: 
Tian Zheng
Date: 
Fri, Dec 4, 2020
Location: 
PIMS, Simon Fraser University
Zoom
Abstract: 

Measuring the impact of scientific articles is important for evaluating the research output of individual scientists, academic institutions, and journals. While citations are raw data for constructing impact measures, there exist biases and potential issues if factors affecting citation patterns are not properly accounted for. In this work, we address the problem of field variation and introduce an article-level metric useful for evaluating individual articles’ visibility. This measure derives from joint probabilistic modeling of the content in the articles and the citations among them using latent Dirichlet allocation (LDA) and the mixed membership stochastic blockmodel (MMSB). Our proposed model provides a visibility metric for individual articles adjusted for field variation in citation rates, a structural understanding of citation behavior in different fields, and article recommendations that take into account article visibility and citation patterns.

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Relations between \(\triangle+\cdots + \triangle + 3\triangle+\cdots + 3\triangle\) and \(\square+\cdots + \square + 3\square+\cdots + 3\square\)

Speaker: 
Zafer Selcuk Aygin
Date: 
Wed, Nov 25, 2020
Location: 
PIMS, University of British Columbia
Zoom
Conference: 
Emergent Research: The PIMS Postdoctoral Fellow Seminar
Abstract: 

See attached PDF

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Accessibility for partially hyperbolic systems

Speaker: 
Todd Fisher
Date: 
Mon, Nov 16, 2020
Location: 
Zoom
University of Utah
Conference: 
Online working seminar in Ergodic Theory
Abstract: 

Accessibility is a fundamental tool when working with partially hyperbolic systems. For instance, in the 1970s it was used as a tool to show certain systems were transitive, and in the 1990s it was used to establish stable ergodicity. We will review the general notion and how it applies in these settings. We will also review the result from 2003 by Dolgopyat and Wilkinson on the C^1 density of stably transitive systems.

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Smooth Realization and Conjugation By Approximation

Speaker: 
Alistair Windsor
Date: 
Mon, Nov 9, 2020
Location: 
Zoom
University of Utah
Conference: 
Online working seminar in Ergodic Theory
Abstract: 

Going back to the foundation work of von Neuman there is a question of whether there are smooth models of the models of classical ergodic theory. When both measure and map are required to be smooth there is only one known obstruction but essentially no general results. Within the class of zero entropy transformation we have a method called conjugation by approximation that can be used to realize many interesting properties. I will describe the method and some of the classical and modern consequences of this.

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The Infinite HaPPY Code

Speaker: 
Monica Jinwoo Kang
Date: 
Wed, Nov 4, 2020
Location: 
University of Saskatchewan
Centre for Quantum Topology and Its Applications
Zoom
Conference: 
quanTA CRG Seminar
Abstract: 

I will construct an infinite-dimensional analog of the HaPPY code as a growing series of stabilizer codes defined respective to their Hilbert spaces. These Hilbert spaces are related by isometries that will be defined during this talk. I will analyze its system in various aspects and discuss its implications in AdS/CFT. Our result hints that the relevance of quantum error correction in quantum gravity may not be limited to the CFT context.

For other events in this series see the quanTA events website.

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PIMS-UNBC Distinguished Colloquium: Benford's Law: Why the IRS might care about the 3x + 1 problem and zeta (s)

Speaker: 
Steven J. Miller
Date: 
Wed, Nov 4, 2020 to Thu, Nov 5, 2020
Location: 
Zoom
University of Northern British Columbia
Abstract: 

Many systems exhibit a digit bias. For example, the first digit base 10 of the Fibonacci numbers or of 2^n equals 1 about 30% of the time; the IRS uses this digit bias to detect fraudulent corporate tax returns. This phenomenon, known as Benford's Law, was first noticed by observing which pages of log tables were most worn from age- it's a good thing there were no calculators 100 years ago! We'll discuss the general theory and application, talk about some fun examples (ranging from the 3x + 1 problem to the Riemann zeta function), and discuss some current open problems suitable for undergraduate research projects.

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Shape Recognition of Convex Bodies

Speaker: 
Sergii Myroshnychenko
Date: 
Wed, Nov 4, 2020
Location: 
PIMS, University of British Columbia
Zoom
Conference: 
Emergent Research: The PIMS Postdoctoral Fellow Seminar
Abstract: 

A broad class of convex geometry problems deals with questions on retrieval of information about (convex) sets from data about different types of their projections, sections, or both. Examples of such assumptions are volume estimates, rigidity of structure, symmetry conditions etc.

In this talk, we will discuss known results and recent developments regarding the dual notions of point-projections and non-central sections of convex bodies. In particular, we provide a partial affirmative answer to the question on a shape recognition posed by A. Kurusa, and discuss a generalization of V. Klee's theorem for polyhedra.

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Turán numbers for a 4-uniform hypergraph

Speaker: 
Karen Gunderson
Date: 
Fri, Nov 6, 2020
Location: 
Zoom
PIMS, University of Victoria
Abstract: 

For any $r\geq 2$, an $r$-uniform hypergraph $\mathcal{H}$, and integer $n$, the \emph{Tur\'{a}n number} for $\mathcal{H}$ is the maximum number of hyperedges in any $r$-uniform hypergraph on $n$ vertices containing no copy of $\mathcal{H}$. While the Tur\'{a}n numbers of graphs are well-understood and exact Tur\'{a}n numbers are known for some classes of graphs, few exact results are known for the cases $r \geq 3$. I will present a construction, using quadratic residues, for an infinite family of hypergraphs having no copy of the $4$-uniform hypergraph on $5$ vertices with $3$ hyperedges, with the maximum number of hyperedges subject to this condition. I will also describe a connection between this construction and a `switching' operation on tournaments, with applications to finding new bounds on Tur\'{a}n numbers for other small hypergraphs.

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