# Computer Science

## Sparse - Dense Phenomena

The dichotomy between sparse and dense structures is one of the profound, yet fuzzy, features of contemporary mathematics and computer science. We present a framework for this phenomenon, which equivalently defines sparsity and density of structures in many different yet equivalent forms, including effective decomposition properties. This has several applications to model theory, algorithm design and, more recently, to structural limits.

## Cryptography: Secrets and Lies, Knowledge and Trust

## How Does Google Google?

**Abstract:**We all Google. You may even have found this talk by Googling. What you may not know is that behind the Google's and other search engines is beautiful and elegant mathematics. In this talk, I will try to explain the workings of page ranking and search engines using only rusty calculus.

**Bio:**Dr. Margot Gerritsen is the Director of the Institute for Computational and Mathematical Engineering at Stanford University. She is also the chair of the SIAM Activity group in Geoscience, the co-director and founder of the Stanford Center of Excellence for Computational Algorithms in Digital Stewardship, and the director of Stanford Yacht Research. She has been appointed to several prestigious positions, including Magne Espedal Professorship at Bergen University, Aldo Leopold Fellow, Faculty Research Fellow at the Clayman Institute and she is also a Stanford Fellow. She is the editor of the Journal of Small Craft Technology and an associate editor of Transport in Porous Media. We are delighted to have Dr. Gerritsen participate in the Mathematics of Planet Earth series.

## How Does Google Google? The Math Behind the Internet

An alternative version of this lecture presented at the University of Calgary is also available.

## Alan Turing, the Politics of Sexual Science, and the Making of a Gay Icon

## Turing and Intelligent Machines

## Alan Turing and Enigma

### Turing 2012 - Calgary

This talk is part of a series celebrating the Alan Turing Centenary in Calgary. The following mathtube videos are part of this series- Alan Turing and the Decision Problem,
*Richard Zach*. - Turing's Real Machine,
*Michael R. Williams*. - Alan Turing and Enigma, John R. Ferris.

## Turing's Real Machines

### Turing 2012 - Calgary

This talk is part of a series celebrating The Alan Turing Centenary in Calgary. The following mathtube videos are also part of this series- Alan Turing and the Decision Problem,
*Richard Zach*. - Turing's Real Machine,
*Michael R. Williams*. - Alan Turing and Enigma,
*John R. Ferris*.

## Alan Turing and the Decision Problem

### Turing 2012 - Calgary

This talk is part of a series celebrating the Alan Turing Centenary in Calgary. The following mathtube videos are also part of this series- Alan Turing and the Decision Problem,
*Richard Zach*. - Turing's Real Machine,
*Michael R. Williams*. - Alan Turing and Enigma,
*John R. Ferris*.

## PIMS Board Meeting - Fall 2011

The PIMS 2011 Fall board meeting was held at the University of Saskatchewan. In addition to the board meeting, board members toured the Canadian Light Source facility.