Graduate Student Seminar

Upcoming Talk

5 March 2021

Problem Solving Without Ansibles: An Introduction to Communication Complexity

Chris Grossack

In the world of Science Fiction, an "ansible" is a device that allows for faster-than-light communication. Without ansibles, interstellar travel puts an interesting constraint on computation. If two planets want to collaborate on solving a problem, the obstruction will likely not be the computation that either planet does individually. Instead, what matters is the *Communication Complexity* which tracks the amount of messages the planets have to send each other to solve their problem. In this talk we will solve a prototypical problem in communication complexity. But be warned: the answer may surprise you!

Winter 2021

12 March 2021

Title TBD

Rahul Rajukmar

5 March 2021

Problem Solving Without Ansibles: An Introduction to Communication Complexity

Chris Grossack

In the world of Science Fiction, an "ansible" is a device that allows for faster-than-light communication. Without ansibles, interstellar travel puts an interesting constraint on computation. If two planets want to collaborate on solving a problem, the obstruction will likely not be the computation that either planet does individually. Instead, what matters is the *Communication Complexity* which tracks the amount of messages the planets have to send each other to solve their problem. In this talk we will solve a prototypical problem in communication complexity. But be warned: the answer may surprise you!

26 February 2021

An Introduction to Orderable Groups

Jonathan Alcaraz 🌍

We call a group (left-)orderable when it admits a left-invariant total order. This simple structure leads to a rich theory with ties to dynamics and topology. In this talk, I'll discuss some examples, useful machinery, and the space of left-orderings.

19 February 2021

MathPeople Study Guide Suite

Alec Martin

For the latter half of my graduate school career I have been playing around with the mechanics of building websites. I also had the fortune to lead the complex qual prep seminar over the past two summers. These two endeavors unavoidably overlapped and I made a website to host the material in the seminar. Naturally I wanted to abstract this project and it has since turned itself into a full fledged (though perhaps not yet finished) web API for integrating study guides into websites. I want to share this project with you fellow educators in the hopes that it may be of interest if you ever want to compile, for yourself or your students, an electronic version of a stack of notecards which has built-in organizational tools and practice test generation. The project is on github at https://github.com/MathPeople/MathPeople.github.io and I will be introducing it and showing how it works in GSS this week.

12 February 2021

Delta Sets of Nonminimally Generated Numerical Monoids

Andrea Stine

A numerical monoid is a subset of \((\mathbb{N}_0,+)\) that is closed under addition, and we can factor elements of a numerical monoid into a monoid's generating elements, which form a generating set. These factorizations are not unique, and invariants such as elasticity and the delta set of these factorizations of numerical monoids have been previously studied. When a non-irreducible element is included in the generating set, the structure of factorizations and factorization invariants may be altered. In minimal geometric generating sets of the form \(\{a^n, a^{n-1}b, ..., ab^{n-1}, b^n\}\), the delta set is simply \(\{b - a\}\). We study the case when a non-irreducible element, labeled \(s\), is added to the generating set. In this specialized instance, we prove several basic properties of the delta set and further characterize the delta sets for particular values of \(s\) and \(b - a\).

5 February 2021

Friday Afternoon Social

29 January 2021

Combatting Academic Distancing during the times of Physical Distance (and normal times too)

Maranda Smith

We will explore what we personally deem to be participation from students, and why we desperately need it as educators. After getting to know what we want and what we don't by way of our classrooms, we can think about various tools to add more of what we like to our everyday discussions. As a talk on participation, this talk will be given via jamboard be prepared to be interactive!

22 January 2021

Why Think? Letting Computers Do Math For Us

Chris Grossack

There are a number of results in logic of the form "If your question can be asked a certain way, then there is an algorithm which tells you the answer". These are called Decidability Theorems, because an algorithm can Decide if a proposition is true or false. In this talk we will survey some results in this area, discuss a few techniques for proving these results, and discuss some open problems are only a few computer cycles away from being solved.

15 January 2021

Resurgence & Fractals

Will Hoffer🌍

In this talk, we shall introduce two modern disciplines of mathematics and discuss current work in intermixing them. Namely, we will give an introduction to the subjects of resurgent asymptotics and to explicit formulae in fractal geometry. The first is a study of asymptotic analysis arising from strengthening Borel resummation. Next, the explicit formulae in fractal geometry are akin to Riemann's explicit formula for the prime counting function, describing geometric and spectral properties of applicable fractals. Our aim is the better understand such formulae, including analytic continuation and studing how their asymptotics change in the complex plane.

Fall 2020

4 December 2020

Eat your Fibers

Christian Williams

Indexing is used throughout math and science -- it's how we organize things in order to analyze or operate on them. There are two ways of thinking about an I-indexed set: a function I -> Set, or a function A -> I. In the latter case, we use preimage to partition the domain into "fibers" over the elements of I. We can think of such a function as a simple example of a "dependent type": for each i in I, there is a type A_i which depends on it.

In this talk, we generalize this to categories! For each ring R, you get a whole category of R-modules: this forms an "indexed category" Mod : Ring^op -> Cat. A functor B^op -> Cat is equivalent to a fibration p : E -> B, a functor with a good notion of preimage. The fiber over each b in B are the types that depend on b, such as R-modules. But now these are categories rather than just sets, so we have morphisms which allow the fibers to interact.

We focus on the example where the fiber over each set is its power set -- this is the canonical model of higher-order predicate logic. The goal is to show that fibrations model foundations: the base category B provides the type theory, and the total category E provides a logic "over" this type theory. (Jacobs' Categorical Logic and Type Theory) I will incorporate how I am using these ideas in my research to generate logics for programming languages.

20 November 2020

The Milnor-Schwartz Lemma and You: Why we care about Geometric Group Theory

Jacob Garcia

The Milnor-Schwartz Lemma roughly states that when a finitely generated group G acts in a nice way on a geodesic metric space X, then the group G is essentially the same as X. The relationship between the generating set of G and the metric on X provides a strong tool for asking, for example, questions about word representations of elements in G, and about the self-isometries on X. In this talk, I will describe what it means for a group to act nicely on a metric space, what it means for a group and a metric space to be essentially the same, and I'll sketch a proof of the Milnor-Schwartz Lemma.

13 November 2020

What does Noble even do?

Noble Williamson

Most of you have probably heard rumors that I do math. Many of you may have even heard rumors that I work on algebraic geometry. This may have raised some concerns given the well-established fact that algebraic geometry is incomprehensible. Between now and when I give this talk I will attempt to figure out what it is that I do and once I do that I will attempt to figure out how to explain it to others. Wish me luck.

6 November 2020

Uniqueness of Kähler structure for \(CP^n\)

Matthew Burns

In this talk, we will focus on many of the cohomological properties that Kähler manifolds enjoy and discuss exactly how formal they are. Three main examples of Kähler manifolds will be emphasized and we will primarily pay attention to complex projective space \(CP^n\). We will also mention important uniqueness results for \(CP^n\) by Hirzebruch-Kodaira-Yau, Kobayashi-Ochiai-Michelsohn, along with Libgober-Wood. Some proofs when n is at most 6 will be included.

30 October 2020

HOMFLY Braid Closures in the Annulus Become Symmetric Functions

Alexander Pokorny

Skein algebras are made up of equivalence classes of link diagrams on a surface where multiplication is given by stacking diagrams. Studying the skein algebra of the annulus is a good first step towards studying other skein algebras; the annulus typically embeds into other surfaces in interesting and sometimes exhaustive ways. To study the annulus, we first study HOMFLY braids and see what their closures look like. Turaev showed that the set of braid closures is isomorphic to the ring of symmetric functions. Furthermore, linear combinations of HOMFLY braids are elements of the (type A) Hecke algebra, which admits a certain family of minimal idempotents. The fact I will discuss is how closures of these idempotents correspond to Schur functions under the Turaev isomorphism. This is the topic of Sascha Lukac's PhD thesis from the early 2000's, which you can find online.

23 October 2020

The Polynomial Method over Finite Fields

George Santellano🌍

The polynomial method is an umbrella term for using polynomials to bound the possible behavior of finite collections of geometric objects such as points, lines, and other hyperplanes with respect to some geometric relation. To understand the polynomial method over finite fields we will give a brief background to the capset theorem on \(\mathbb{F}_3^4\) and prove it in the method of Dvir. We will also introduce the finite field kakeya theorem and prove it in the method of Ellenberg and Gijswijt.

16 October 2020

Fractals and Taylor Series Expansion

Matthew Overduin

In this talk, I will present some preliminary results regarding the error term in the generalized Taylor series expansions for distributions or generalized functions. We will first uncover what happens when our generalized function is an actual function that is continuous up to order \(k\). The error term in this particular case should coincide with the error term in the normal Taylor series expansion of the function.

9 October 2020

Model Theory and You: Infinite Proofs for Free

Chris Grossack

Model Theory is the branch of mathematical logic that deals with "truth" in axiomatic structures. Perhaps surprisingly, Model Theory is extremely insensitive to the notion of cardinality, and we can leverage this insensitivity to prove infinite theorems by considering only finite objects. In this talk we will discuss the fundamentals of Model Theory, as well as the Logical Compactness theorem, which we will use to prove theorems in combinatorics and algebra. Time permitting, we will state the Lowenheim-Skolem Theorem, and outline some potential applications.

The UC Riverside Math Graduate Student Seminar (GSS) is brought to you by the UCR student chapter of the American Mathematics Society. GSS is organized by the officers of the chapter.

Officers

Maranda Smith, President

Jonathan Alcaraz, Vice President

Noble Williamson, Secretary

Alec Martin, Treasurer

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