# Seminar

This seminar is intended for an undergraduate audience. If you have an interesting talk that would be suitable for undergrads, feel free to contact the organizers and volunteer as a speaker. We especially appreciate talks by undergrads for undergrads!

Seminar runs Wednesdays 13-14:00 (EST) in IC 318 at UTSC and on Zoom. We start seminar at 13:05, to let people arrive and get settled.

After attending seminar, we ask that participants fill out this feedback form. If you are not able to use Google Forms and would still like to give feedback, please e-mail the organizers.

The *prime factorization* of the Meeting ID is: $11 \times 59 \times
124877917$. The passcode for the meeting is: seminar. If you have trouble
accessing the seminar, please contact the co-organizers: Parker Glynn-Adey and
Lisa Jeffery. We will send you a direct
link.

Io you want to receive regular announcements about Seminar, please sign up for our ListServ. We’re also listed on ResearchSeminars.org which you can add to your Google Calendar.

At the bottom of this page, there FAQ for speakers.

# Draft Winter 2023 Schedule

Date | Speaker | Title | Notes | Attendees (online + in-person) |
---|---|---|---|---|

January 19 | Anatoly Zavyalov | Automatic Sequences | ||

January 26 | Maitreyo Bhattacharjee | The Topelitz Conjecture | ||

February 2 | Daniel Harrington | |||

February 9 | Erik Tou | |||

February 16 | Justin Fus | |||

March 2 | Andrew Feng | |||

March 9 | Logan Lim | |||

March 16 | Aditya Chugh | |||

March 23 | Lisa’s Students: Sharon Alex et al. | |||

March 30 | Reserved for Reading Courses |
|||

April 6 | Reserved for Reading Courses |

# Fall 2022 Schedule

Date | Speaker | Title | Notes | Attendees (online + in-person) |
---|---|---|---|---|

September 14 | Brent Pym | Periods: from pendula to the present | video / slides | 6 + 7 |

September 21 (online only) | Zack Wolske | An Introduction to Combinatorial Games | video / slides | 25 |

October 5 | Scott Carter | Permutations with quipu | video / slides / paper | 9 + 11 |

October 12 | Reading Week | |||

October 19 | Blake Madill | An Algebraic Proof of the Fundamental Theorem of Algebra | video / slides | 11 + 7 |

October 26 | Sarah Brewer | Star rosettes in GeoGebra: constructing traditional patterns with contemporary technologies | video / slides / paper / GeoGebra | 10 + 8 |

November 2 | Alex Teeter | Spheres, Donuts and Crazy Bottles: An Introduction to The Classification Theorem of Surfaces | video / slides | 8 + 12 |

November 9 | Ben Briggs | What’s the deal with Homological Algebra? | video / slides | 8 + 21 |

November 16 | Özgür Esentepe | What caused Coxeter many restless nights? | video / slides | |

November 23 | Brian Zhengyu Li | A SAT Solver + Computer Algebra Attack on the Minimal Kochen-Specker Problem | slides / video | 8 + 8 |

November 30 | Albert Lai | An Introduction to Intuitionistic Logic | slides / lean |

### September 14: Periods: from pendula to the present by Brent Pym

*Abstract*:
Many important quantities can be expressed as integrals whose domain and integrand are determined by polynomials with rational coefficients.
Such numbers, which include $\sqrt{2}$, $\log(7)$, $\pi$, etc. are called “periods”, because their systematic study was inspired, in part, by the classical calculation of the period of oscillation of a pendulum.
Despite the apparent simplicity of the definition, periods have a rich and beautiful structure, and are the subject of some of the deepest open problems in mathematics, connecting geometry, algebra, number theory, physics and more.

I will give an introduction to this circle of ideas and the questions that drive current research in the area, assuming only basic knowledge of multivariable calculus.

### September 21: An Introduction to Combinatorial Games by Zack Wolske

*Abstract*:
We’ll introduce a collection of two player games that anyone can play – they’re fun for all ages.
Some games have strategy patterns we can find quickly, some have well-hidden patterns that we can uncover with more tools, and others have patterns that no one in the world has found.
We will play and analyze those games and share currently open problems.

### October 5: Permutations with quipu by Scott Carter

*Abstract*:
According to Wikipedia, a quipu is an accounting system in which knots are tied in a sequence of strings.
They were used as a method of storing tax and other financial records.
Here we consider cyclic subgroups of groups and catalogue the cosets by means of a string bundle (the English word, not the mathematical word is intended).
The quipu are elements in the cyclic subgroups.
The traditional methods of multiplying braids by means of vertical juxtaposition is mimicked in the case of permutations-with-quipu.
The quipu are allowed to pass upwards through the crossings of transverse strings.
So a permutation-with-quipu represents an element in a semi-direct product.

We have developed appealing diagrams that represent the elements in the dihedral groups, and especially in the finite subgroups of SU(2). Have no fear! The groups in question will be described explicitly, and we’ll play with the diagrams in ways that allow easy computations. In fact, the permutations-with-quipu can be thought of as matrices in disguise. I will show how to go between the quipu and the corresponding matrices. Emphasis will be upon examples.

### October 19: An Algebraic Proof of the Fundamental Theorem of Algebra by Blake Madill

*Abstract*:
Recall that the Fundamental Theorem of Algebra states that every non-constant polynomial over the complex numbers completely factors as a product of linear terms.
In a typical undergraduate experience, students will see proofs of this theorem using topology and/or complex analysis.
In this talk, we will explore a completely algebraic (with the exception of some basic calculus) proof of this algebraic theorem.
Students will be introduced to aspects of group theory, Sylow theory, field theory, and Galois theory.
No prior knowledge of abstract algebra will be assumed.

### October 26: Star rosettes in GeoGebra: constructing traditional patterns with contemporary technologies by Sarah Brewer

*Abstract*:
Star rosette patterns are ubiquitous in geometric architectural ornament of the Islamic world.
These patterns are traditionally built on a mathematically elegant system of polygons and tangent circles in their underlying Euclidean compass and straightedge constructions.
Of particular interest are star rosette patterns built on univalent circle packings whose intersection graph is any k-uniform tiling, where varying the angle of the star rosette pattern lines serves as the transition between a tiling and its dual.
In simple terms, you’ll learn how to make some pretty patterns in GeoGebra.

### November 2: Spheres, Donuts and Crazy Bottles: An Introduction to The Classification Theorem of Surfaces by Alex Teeter

*Abstract*:
Mathematicians love to classify mathematical structures in order to understand them better.
In this presentation, I will take you on a journey through the World of Surfaces and prove their classification.
We will see many examples of Surfaces, such as the one-sided Mobius Strip, the Torus, and the Klein Bottle, a bizarre surface that cannot be embedded in 3-dimensional space.
We will also cover how to construct surfaces easily and conveniently using surgery, and prove that all surfaces (that fulfill certain conditions) can be constructed from such surgery.
I hope you are excited as I am to delve into the wonderful world of Topology!

No prior knowledge of Topology is needed.

### November 9: What’s the deal with Homological Algebra? by Ben Briggs

*Abstract*:
Back in the 70’s, David Mumford accused algebraic geometry of “secretly plotting to take over all the rest of mathematics”.
While that battle was raging, the topologists attacked from the side and annexed most of algebra (as well as a good deal of number theory, combinatorics, statistics, physics).
Nowadays you cannot go outside without stepping in homology or cohomology, or some kind of homotopy.
All of this started from homological algebra (the Trojan horse?), which sort of began with David Hilbert and Emmy Noether way back in the 1890’s, but which really got going in the 50’s.
I will explain what homological algebra is in very gentle terms, starting with chain complexes, and I’ll give a lot of concrete examples of the cool things you can do with it.
I might also give a less concrete idea of how it ended up everywhere (or at least, in math I do).

### November 16: What caused Coxeter many restless nights? by Özgür Esentepe

*Abstract*:
“Frieze patterns” kept Coxeter up at night.
This talk will introduce these surprisingly ubiquitous grids of integers.
We will discuss some basic properties and how they appear in representation theory.
We will assume almost zero background.

### November 23: A SAT Solver + Computer Algebra Attack on the Minimal Kochen-Specker Problem by Brian Zhengyu Li

*Abstract*:
One of the most fundamental results in the foundations of quantum mechanics is the Kochen-Specker (KS) theorem, a `no-go’ theorem that states that contextuality is an essential feature of any hidden-variable theory.
The theorem hinges on the existence of a mathematical object called a KS vector system.
While the existence of a KS vector system was first established by Kochen and Specker, the problem of the minimum size of such a system has stubbornly remained open for over 50 years.
In this paper, we present a new method that is based on a combination of a SAT solver and a computer algebra system (CAS) to address this problem.
Using our approach, we improve the lower bound from 22 to 23, with a significant speed-up over the most recent computational methods.
Finding the minimum KS system could enable applications in security of quantum cryptographic protocols, zero-error classical communication, and dimension witnessing.

### November 30: An Introduction to Modal Logic and Its Applications by Jesse Maltese

*Abstract*:
Modal logic refers to an extension of the language of classical logic wherein two new operators are added.

Referred to as modal operators and denoted $\square$ and $\lozenge$ (‘box’ and ‘diamond’ respectively), these operators change the truth value of a proposition, allowing one to reason about modalities such as necessity, knowledge, and time.

This talk will first present some of the historical development of modal logic, and then introduce the Kripke semantics.
We will talk briefly of some alternative semantics, before presenting other modal logics, specifically temporal, epistemic, and doxastic.
We will conclude with a discussion of the applications of these systems of logic to computer science.
Specifically, how they are used to reason about distributed systems and concurrent programs, and for verifying correctness of software.
Throughout, we will make note of the philosophical applications.

This talk will assume an understanding of first-order logic.

### TBD: Speedrunning Differential Geometry by Davide Radaelli

*Abstract*:
In this talk, I’ll be speedrunning as much of differential geometry as I can, building everything up from first-principles.
I’ll start off with logic, then move onto set theory, topology, manifolds, bundles, linear algebra, tangent spaces, tensors, differential forms, connections and more.

### TBD: Dr. Kripke And The Multiverse of Logics by Albert Lai

*Abstract*:
I will introduce and motivate some extensions of basic (classical proposition or first-order) logic and how to formalize their meanings.

Specifically:
Intuitionistic logics insist that a proof of a statement should be also a recipe for outputting a witness to that statement, and thus reject that, e.g., “P or not P” can be proved unless tailor-made to a specific P.
Modal logics start with basic logic (propositional logic) and adds unary operators intended to mean “necessarily” and “possibly”, to help express “John must be sleeping” and “John may be sleeping”.
Temporal logics have a state transition system in mind, and starts with basic logic and adds unary operators intended to mean “for every state in the next step”, “for some state in the next step”, “for every step from now on”, “infinitely often”, etc.

They have evident applications in verification of program correctness.
We understand the semantics (meaning) of a logic by imagining a mapping from symbolic names (e.g., the propositional variable “P” above) to concrete things, and asking how the logical operators evaluate the latter.

In the 1960’s, the then open question of giving semantics to modal logics and intuitionistic logics were both solved by Saul Kripke (as a young prodigy) in one stroke by the same idea of:
What if there are multiple (but connected) worlds, and different worlds can have different mappings; naturally, the idea carries over to temporal logics (which arose after Kripke’s solution).

I will introduce said logics and explain Kripke’s solution by a multiverse of, uh, truths!

# Winter 2022 Seminar

Date | Speaker | Title | Notes | Attendees |
---|---|---|---|---|

February 2 | Parker Glynn-Adey | Organizational Meeting | 12 | |

February 9 | Kitty Yan, Japleen Anand, and Logan Murphy | Getting Started: Proving with the Lean Interactive Theorem Prover | 20 | |

March 16 | Kevin Santos | Modelling Mathematics with Knitting and Crochet | video / slides | 16 |

March 23 | Logan Lim | Why Geometric Algebra Should be in the Standard Linear Algebra Curriculum | video / slides | 22 |

March 30 | Alex Teeter | Seifert Surfaces and Knot Genus | video / slides | 24 |

### March 16: Modelling Mathematics with Knitting and Crochet by Kevin Santos

*Abstract*:

When studying subjects like geometry and topology, it can be difficult to visualize or understand certain abstract concepts. Being able to hold and manipulate a physical model of a mathematical object can give deeper intuition into its properties. The process of constructing such an object also offers further insight. In this talk, we will investigate how geometric and topological objects can be constructed using the crafts of knitting and crochet, which offer unique advantages in creating models. We will describe how the hyperbolic plane can be modelled with crochet and we will explore how topological surfaces such as the sphere, the torus, and the Klein bottle can be knitted. No prior knowledge in geometry, topology, knitting, or crochet is required.

### March 23: Why Geometric Algebra Should be in the Standard Linear Algebra Curriculum by Logan Lim

*Abstract*:

Geometric algebra is an extension of $\mathbb{R}^n$ that includes as special cases: The complex numbers, quaternions, exterior algebras, dual numbers, split-complex numbers, dual quaternions and more! When applied to multivariable calculus, it generalizes the fundamental theorem of calculus on manifolds to include the divergence theorem, curl theorem, and gradient theorem, and as a result Green’s and Stoke’s theorem, as special cases of a single statement. It also simplifies many geometric operations in computer graphics by eliminating the need for matrices in projections, rotations, and reflections. Though we can only cover the ‘main idea’ of geometric algebra in the allotted time, this talk will be a buffet of ideas you can explore for this fascinating and deceptively simple algebraic object.

Mathematicians hate him!!!! See how Clifford generalized rotations and orthogonal complements in n-dimensions with this one simple trick! $$ \mathbf{uv} = \mathbf{u} \cdot \mathbf{v} + \mathbf{u} \wedge \mathbf{v}. $$

### March 30: Seifert Surfaces and Knot Genus by Alex Teeter

*Abstract*:

Knot Theory, a field of mathematics born from a misguided model for atoms, has since grown to become an important subfield of Topology. Not only does it have much of mathematical interest, but also numerous connections to fields such as graph theory, the study of manifolds, and applications to Biology and Physics. We will analyze the connection between Knot Theory and the Topology of Surfaces. Along the way, we will cover the Euler Characteristic, Genus and the beautiful Classification Theorem of Surfaces. Through this consideration, we develop an algorithm to associate each Knot with a surface, and uncover an important invariant, the Genus of a Knot. This will not only allow us to distinguish between different Knots, but will also be vital in establishing fundamental properties of prime and composite Knots. No prior background in Knot Theory or Topology is assumed.

# Fall 2021 Seminar

Date | Speaker | Title | Notes | Attendees |
---|---|---|---|---|

Nov 10 @ 11:10-11:59am EST | Zhekai Pang and Yuhong Zhang | Matrix Analysis with a Focus on Inequalities | video / slides | 22 |

Nov 17 | Mathew Cater Benavides | An Introduction to the Fractional Brownian Motion | video / slides | 11 |

Nov 24 | Kitty Yan, Japleen Anand, and Logan Murphy | Getting Started: Proving with the Lean Interactive Theorem Prover | video / slides | 25 |

Dec 1 | Kitty Yan, Japleen Anand, and Logan Murphy | Getting Started: Proving with the Lean Interactive Theorem Prover | video / slides | 18 |

### November 17: Fractional Brownian Motion

*Abstract*:
The classical Brownian motion (or Wiener process) serves as the fundamental
object of probability theory with vast theoretical and practical applications
in a plethora of fields. In the early 1940’s Kolmogorov sought a natural one
parameter extension of the process in aims of modelling turbulence in liquids,
the extension consists of retaining the framework of the classical motion by
constructing still a continuous centered Gaussian process that retains self
similarity (of a now distinct index from that of the classical motion) and
stationarity of increments but draws its distinction by parameterizing its
specifying covariance structure with what is known as the Hurst index, $H \in
(0,1)$, resulting in (for ‘most’ values of $H$) a non-Markov process allowing it
to serve as a popular model for dependent phenomena; this extension has since
been kept in common parlance as fractional Brownian motion (fBm). This talk
aims to provide discussion and (at times demonstration) of the fundamental
properties of the fBm as well as investigate sample path properties’ dependence
on the Hurst parameter.

### November 10: Matrix Analysis with a Focus on Inequalities

*Abstract*: Matrix inequalities are one of the key components in matrix
analysis. They have a wide range of applications in statistics, computer
science, economics, and physics.

In this presentation, we focus on some classical matrix inequalities such as the Rayleigh-Ritz quotient, the Courant Fischer theorem, Weyl’s inequality, the interlocking eigenvalue lemma, and the Woodbury matrix identity. In particular, some of these show the importance of the maximum and minimum of eigenvalues and singular values.

Recommend Background: Linear Algebra and Calculus. (In the beginning of the presentation, some definitions and key properties such as positive definiteness will be reviewed.)

### November 24: Getting Started: Proving with the Lean Interactive Theorem Prover

*Abstract:* Have you heard of automated and interactive theorem provers? Did you know that American mathematician Alex Kontorovich predicts that the Lean Interactive Theorem Prover will be so widely used that it will be as necessary as LaTex in doing mathematics? This seminar series will take you on a journey, using Lean to give you insights on how to go about proving, which route to choose, how to check for errors, and how to verify a computation or a proof. Particularly, you will be learning to use Lean by playing a number game. Come join us and have some fun!

# Summer 2021 Seminar

Date | Speaker | Title | Notes |
---|---|---|---|

May 26 | Brian Li | Cops and Robbers with Many Variants | video / slides |

June 2 | Parker Glynn-Adey | The Probabilistic Method | video / slides |

June 9 | Ben Chislett | Ray Tracing and the Light Transport Equation | video / slides |

June 16 | Jesse Maltese | An Introduction to Mathematical Logic | video / slides |

June 23 | David Schrittesser | Your life will be better with infinitesimals (Part 1) | video |

June 30 | David Schrittesser | Your life will be better with infinitesimals (Part 2) | Cancelled |

July 7 | Yuveshen Mooroogen | Shining a rainbow-coloured light on the fundamental theorem of algebra | video / slides |

July 14 | Albert Lai | Partial orders and application to semantics of computer programs | video / slides |

July 21 | Kevin Santos | An Introduction to Group Theory through Puzzles | video / slides |

July 28 | Rakan Omar (York) | Influence Centrality | video / slides |

August 4 | Andrew Fallone (York) | The Projected Number of Underreported COVID 19 Cases in Canada | No slides or recording available, due to technical issues |

August 11 | Julie Midroni | Artificial neural networks: The fundamentals | video / slides |

August 18 | Jiawei Chen, Ran Li and Junru Lin | Rapid Testing in COVID and Modified SIR Model | video / slides |

Friday August 20 |
Richard Ye and Xin Ya Xu | Hero Rats - Detecting Tuberculosis | video / slides |

August 25 | Amalrose Vayalinkal | Virtual Ring Routing | video / slides |

We are listed on ResearchSeminars.org as UndergraduateSeminar.

## Speakers

### August 25: Amalrose Vayalinkal: Virtual Ring Routing

*Abstract*:

Virtual Ring Routing (VRR) schemes define a routing algorithm for communication between devices by establishing a virtual network overlay given a physical network of $N$ devices. Using graphs to model the physical network, we introduce the algorithm and explore the pros and cons of VRR. Time permitting, we take a closer look at the simpler case where the physical network is also a ring (circle) and discuss future directions. This work is part of an NSERC USRA this summer under the supervision of Professor Almut Burchard.

**FRIDAY** August 20: Xin Ya Xu and Richard Ye: Hero Rats - Detecting Tuberculosis

*Abstract*:

Tuberculosis has been the leading infectious killer in the world with an infection rate of approximately 10 million people per year. Slow and inaccurate detection methods contribute heavily to making tuberculosis so deadly. In this talk, we will highlight the efforts of APOPO, a non-profit organization that trains scent-detecting African giant pouched rats, to tackle tuberculosis. We will also talk about our approach to improve APOPO’s scent detection technology by using statistical analysis. We will explore the process of applying clustering techniques, such as hierarchical clustering and K-means clustering, to the problem.

Work by Xin Ya Xu and Richard Ye, supervised by Professor Sohee Kang and Professor Marco Pollanen. This is a project where the data was brought to us by Professor Pollanen who works with APOPO, a firm focused on detecting land mines and tuberculosis mainly in sub-saharan Africa.

### August 18: Jiawei Chen, Ran Li and Junru Lin: Rapid Testing in COVID and Modified SIR Model

*Abstract*:

The traditional PCR test for coronavirus typically takes one day to produce results, which cannot satisfy the great volume of demand for testing. However, the recently developed “Rapid Test” (which detects Covid antigen) can help us obtain reasonably accurate results in about 15 minutes. In this talk, we will use a modified SIR model (a classical ODE system for modelling epidemic) to demonstrate how the dynamics of Covid-19 can be affected under the introduction of this new testing technique. We will then discuss how effective the test needs to be in order to control the pandemic.

### August 11: Julie Midroni: Artificial neural networks: The fundamentals

*Abstract*:

Artificial neural networks (ANNs) are a powerful class of machine learning algorithms that can be used for a variety of purposes, including image classification, function approximation, and natural language processing. This talk will present the mathematical basics of ANNs, and briefly explore different ANN algorithms and their uses.

### August 4: Andrew Fallone: The Projected Number of Underreported COVID 19 Cases in Canada

*Abstract*:

As Canada focuses more on mitigation strategies rather than eradication ones, mathematical modelling could play an important role in preserving lives. The model used in this project is a modified SIR model which retains a conservative calculation for COVID 19 cases while giving an insight into how unreported COVID 19 cases are in Canada with the assumption that we have a limited amount of data. This approach seems to be the most effective due to the uncertainty of COVID 19 progression in Canada. Furthermore, this modified SIR model uses a basic reproduction parameter “to estimate the attack rate, epidemic duration”, and critical points of COVID 19 cases in Canada.

### July 28: Rakan Omar: Influence Centrality

*Abstract*:

In graph theory and network analysis, the notion of centrality refers to assigning nodes in a network an index representing the extent to which each node is central - important to the network, or well positioned in it - based on some mathematical property. There are a variety of measures of centrality, each of which measures ‘centrality’ differently, based on (or resulting in) a different definition of ‘importance’ or ‘prominence’.

I will define an original measure of centrality, a variation of pageRank centrality, which I call ‘influence centrality’, that measures the extent to which a node contributes a relation (what is represented by the arcs) to the graph in a directed weighted graph with a finite number of nodes, which are initially labelled with values. I will discuss some properties, applications, and extensions of influence centrality.

I assume some familiarity with graph theory terminology and linear algebra.

### July 21: Kevin Santos: An Introduction to Group Theory through Puzzles

*Abstract*:

The concept of a group is a powerful tool that we can use to understand the structures of mathematical objects. In this talk, we’ll use well-known puzzles such as Peg Solitaire, the 15 puzzle, and Rubik’s cube to motivate a brief introduction to the concepts of group theory. We’ll explore how groups are related to symmetry and give some examples of groups, such as the Klein 4-group and the permutation groups. We’ll then see how these ideas can be applied to understand the puzzles.

### July 14: Albert Lai: Partial Orders and Application to the Semantics of Computer Programs

*Abstract*:

Partial orders generalize total orders by allowing all four possibilities: $x<y$, $x>y$, $x=y$, or none of the above. (Total orders disallow the fourth possibility.) A familiar example is the subset relation over a family of sets. I will show a computer-science application of partial orders to modelling recursive programs. This will be a glimpse of denotational semantics, the study of describing program behaviour by mapping programs to suitable mathematical structures and partial orders.

### July 7: Yuveshen Mooroogen: Shining a rainbow-coloured light on the fundamental theorem of algebra

*Abstract*:

The graphs of real-valued functions on the real line are subsets of a two-dimensional space. As a result, we can sketch them on a piece of paper.

The graphs of complex-valued functions on the complex plane, however, are subsets of a four-dimensional space. Good luck sketching that on a piece of paper.

In this presentation, I will introduce “domain colouring”, which is a technique used to illustrate functions of the complex numbers.

This talk will be in two parts. In the first part, I will explain how to read and construct domain colouring plots, focusing on a number of simple examples. In the second part, I will discuss the Fundamental Theorem of Algebra (which states that every nonconstant polynomial has a complex root) and explain how to visualise one of its proofs using domain colouring. This part of the talk will draw heavily from D. J. Velleman’s beautiful expository article [1].

Prerequisites: Familiarity with the concept of dimension (for a vector space) and with the complex numbers. (Basic principles only. You should know what the notation $x + iy$ means, and how to convert it to modulus-argument/polar form.) Knowledge of multivariable calculus and complex analysis is not expected.

[1] Velleman, D.J. The Fundamental Theorem of Algebra: A Visual Approach. Math Intelligencer 37, 12–21 (2015). https://doi.org/10.1007/s00283-015-9572-7.

### June 23 and 30: David Schrittesser: Your life will be better with infinitesimals

*Abstract*:
When Leibniz, Newton, and others first developed calculus, they used the
metaphor of infinitely small, or infinitesimal, quantities to try to justify
their methods. Later, infinitesimals were expelled from mathematics and
calculus was made rigorous using the familiar notions of limit and
epsilon-delta formulations.

But infinitesimals have been making a come back! Using methods from logic, in particular model theory, they have been restored as respected citizens in rigorous mathematical arguments. This approach, called non-standard analysis has been described as ``the analysis of the future’'. And indeed, it sometimes allows us to do miraculous things. A recent case in point is my joint result with D. Roy and H. Duanmu, with which we solve a long-standing open problem in statistics (namely giving a Bayesian interpretation of admissibility).

In this talk I will give an introduction to the non-standard method and describe some applications. (And if I manage to spark your interest, come to the course I will teach about this topic at U of T in this fall!)

### June 16: Jesse Maltese: An Introduction to Mathematical Logic

*Abstract*:

In this talk, I will give an introduction to the various ideas underlying the foundations of math. I will first talk through some of the history of the field. Then, I will introduce basic concepts in logic including the definition of truth, a model, and notions like completeness and consistency. Then, I will state two important theorems in the field: Gödel’s Completeness Theorem, and the Compactness Theorem. Finally, I will give some interesting applications of compactness, namely the infinite four-colour theorem and the Ax-Grothendieck Theorem.

### June 9: Ben Chislett: Ray Tracing and the Light Transport Equation

*Abstract*:

Ray Tracing is the primary technique for rendering photorealistic images. Advancements in ray tracing techniques have enabled its use in a variety of computer graphics applications, from animated films to real-time video games. In this talk, we explore the Light Transport Equation, Monte Carlo integration, and some of the many optimizations that have led to ray tracing’s rapid rise in popularity.

### June 2: Parker Glynn-Adey: The Probabilistic Method

*Abstract*:

Mathematicians love purity, intuition, and clarity. We like to construct things explicitly with no messiness. But sometimes, mathematical reality is too weird for our explicit methods. Sometimes, we need to look at random examples to find what we’re looking for. In this talk, we use randomness to produce colourings of complete graphs with no monochromatic cliques, a foundational example of the probabilistic method pioneered by Paul Erdős.

Background in counting and graph theory at the MAT A67 / MAT 202 level will help.

### May 26: Brian Li: Cops and Robbers with Many Variants

*Abstract*:

Mathematics and games complement each other in both mathematical research and learning. Cops and Robbers is a game played on graphs between a set of cops and a single robber. The cops begin the game by moving to a set of vertices, with the robber then choosing a vertex to occupy. All players move from vertex-to-vertex along edges. The cops win by successfully occupying the robber’s vertex, hence catching the robber. We will discuss theorems that help us better understand such games and unleash our creativity to explore many different variants. No prior knowledge required.

## FAQ

- How long should my talk last?
- The longest possible talk is 50 minutes, which allows for five minutes for people to arrive and five minutes for questions. Feel free to use up to 50 minutes. Any talk in the range 15 to 50 minutes would be great.

- Do I need to use a particular format for my slides?
- No, feel free to use any software that you like to make your slides. You don’t even need to make slides. Feel free to draw, or use a whiteboard. For math talks, lots of speakers use Beamer.

- Will my talk be recorded and shared online?
- By default, yes and yes. The talks are recorded to Zoom Cloud and
then Parker edits the recording and puts it on YouTube. If you do
**not**want your talk put online, please let Parker know. He will not post your talk online. We want you to feel comfortable speaking and will accodomate privacy concerns.

- By default, yes and yes. The talks are recorded to Zoom Cloud and
then Parker edits the recording and puts it on YouTube. If you do
- Do I need to present original research?
- No! Feel free to present anything. We especially appreciate introductory talks, which introduce the audience to an novel topic. If you have original research that you would like to present, then please do so in a friendly and introductory manner.

- Do you have any suggestions for things to present?
- Jocelyn R. Bell & Frank Wattenberg (2020) The Slippery Duck Theorem, Mathematics Magazine, 93:2, 91-103, DOI: 10.1080/0025570X.2020.1708693
- Sam Chow, Ayla Gafni & Paul Gafni (2021) Connecting the Dots: Maximal Polygons on a Square Grid, Mathematics Magazine, 94:2, 118-124, DOI: 10.1080/0025570X.2021.1869493
- Bhargava, Manjul. “The factorial function and generalizations.” The American Mathematical Monthly 107.9 (2000): 783-799.pdf
- Birman, Joan S. “New points of view in knot theory.” Bulletin of the American Mathematical Society 28.2 (1993): 253-287. pdf
- Margalit, Dan. “The Mathematics of Joan Birman.” Notices of the American Mathematical Society (2019). pdf