Monday 9/21
 No Seminars
Tuesday 9/22
 No Seminars
Wednesday 9/23
 No Seminars
Thursday 9/24
 No Seminars
Friday 9/25
 No Seminars
Weekly Seminars
Seminar Schedule for Fall 2020  All Seminars are Through Zoom
Mondays
Modeling in Biology & Physics  Dr. Qixuan Wang  12:30  1:50 p.m.
Tuesdays
Fractal Geometry, Complex Dimensions & Zeta Functions  Dr. Michel Lapidus  9:30  10:50 a.m.
Algebraic Geometry  Dr. Jose Gonzalez  11:00 a.m.  12:20 p.m.
Lie Theory  Dr. Vyjayanthi Chari  12:30  1:50 p.m.
Interdisciplinary Center for Quantitative Modeling in Biology Seminar  Dr. Mark Alber  2:00  3:20 p.m.
Wednesdays
Partial Differential Equations & Applied Math  Dr. Yat Tin Chow & Dr. Jia Gou  10:00  10:50 a.m.
Combinatorial Number Theory  Dr. MeiChu Chang  11:00  11:50 a.m.
Topology  Dr. Stefano Vidussi  12:00 noon  12:50 p.m.
Modeling in Biology & Physics  Dr. Qixuan Wang  12:30  1:50 p.m.
Operator Algebras & Related Topics  Dr. Feng Xu  1:00  1:50 p.m.
Thursdays
Fractal Geometry, Complex Dimension & Zeta Functions  Dr. Michel Lapidus  9:30  10:50 a.m.
Lie Theory  Dr. Vyjayanthi Chari  12:30  1:50 p.m.
Fridays
Differential Geometry  Dr. Fred Wilhelm  11:00  11:50 a.m.
Commutative Algebra  Dr. Eloisa Grifo  2:00  2:50 p.m.
Ergodic Theory & Spectral Theory  Dr. Zhenghe Zhang  2:00  2:50 p.m.
Extended Seminar Schedules
These are provided by the coordinators. Not all seminars have extended schedules available.
Algebraic Geometry
The UC Riverside Algebraic Geometry Seminar meets on Tuesdays from 11:00am to 12:00pm in Skye 268. For more information you may contact Ziv Ran (ziv.ran@ucr.edu) or Jose Gonzalez (jose.gonzalez@ucr.edu). Please find our schedule below. For information about reimbursements for our visitors click here.
Winter 2020
Date  Speaker  Title  Abstract 
Tuesday, January 7, 2020 Start: 11:00 AM Location: Skye 268 
Planning meeting.  Planning meeting.  
Tuesday, January 14, 2020 Start: 11:00 AM Location: Skye 268 
Noble Williamson UC Riverside 
A crash course in algebraic geometry.  As we begin to explore geometric invariant theory (GIT), it will be useful to establish a sturdy foundation off of which we can build. In this talk, we will cover some of the fundamental concepts of algebraic geometry that will be important to understand the deeper theory to come. We will start by defining affine and projective varieties, some of the main objects of study in algebraic geometry, and we will work our way to establishing morphisms of varieties. This talk is meant to be as accessible as possible and assumes no prerequisite knowledge other than a very basic understanding of rings and ideals. 
Tuesday, January 21, 2020 Start: 11:00 AM Location: Skye 268 
Ethan Kowalenko UC Riverside 
Algebraic groups.  In this talk we will go over the definitions and some of the basics of representations of algebraic groups, with a focus on linearly reductive algebraic groups. 
Category Theory
Category Theory Website
15 Apr: Jules Hedges  Open Games: The long road to practical applications
Abstract: I will talk about open games, and the closely related concepts of lenses/optics and open learners. My goal is to report on the successes and failures of an ongoing effort to try to realise the oftenclaimed benefits of categories and compositionality in actual practice. I will introduce what little theory is needed along the way. Here are some things I plan to talk about:
 Lenses as an abstraction of the chain rule
 Comb diagrams
 Surprising applications of open games: Bayesian inference, value function iteration
 The state of tool support
 Open games in their natural habitat: microeconomics
 Sociological aspects of working with economics
22 Apr: Michael Shulman  StarAutonomous Envelopes
Abstract: Symmetric monoidal categories with duals, a.k.a. compact monoidal categories, have a pleasing string diagram calculus. In particular, any compact monoidal category is closed with [A,B] = (A* ⊗ B), and the transpose of A ⊗ B → C to A → [B,C] is represented by simply bending a string. Unfortunately, a closed symmetric monoidal category cannot even be embedded fullyfaithfully into a compact one unless it is traced; and while string diagram calculi for closed monoidal categories have been proposed, they are more complicated, e.g. with "clasps" and "bubbles". In this talk we obtain a string diagram calculus for closed symmetric monoidal categories that looks almost like the compact case, by fully embedding any such category in a starautonomous one (via a functor that preserves the closed structure) and using the known string diagram calculus for starautonomous categories. No knowledge of starautonomous categories will be assumed.
29 Apr: Gershom Bazerman  A localic approach to the semantics of dependency, conflict, and concurrency
Abstract: Petri nets have been of interest to applied category theory for some time. Back in the 1980s, one approach to their semantics was given by algebraic gadgets called "event structures." We use classical techniques from order theory to study event structures without conflict restrictions (which we term "dependency structures with choice") by their associated "traces", which let us establish a onetoone correspondence between DSCs and a certain class of locales. These locales have an internal logic of reachability, which can be equipped with "versioning" modalities that let us abstract away certain unnecessary detail from an underlying DSC. With this in hand we can give a general notion of what it means to "solve a dependency problem" and combinatorial results bounding the complexity of this. Time permitting, I will sketch workinprogress which hopes to equip these locales with a notion of conflict, letting us capture the full semantics of general event structures in the form of homological data, thus providing one avenue to the topological semantics of concurrent systems. This is joint work with Raymond Puzio.
6 May: Sarah RovnerFrydman  Separation Logic Through a New Lens
Abstract TBA
13 May: TaiDanae Bradley  TBD
20 May: Gordon Plotkin  TBD
3 June: Nina Otter  TBD
Fractal Research Group
Weekly Seminars on Thursdays in Surge 268:
 FRG (Fractal Research Group) Seminar: 11:00 am 12:20 pm.
 MPDS (Mathematical Physics & Dynamical Systems) Seminar: 3:304:50 pm.
More detailed information (such as speakers, titles, abstracts & workshops) are available in the google calendar below.
Graduate Student Seminar
Graduate Student Seminar
UC Riverside AMS student chapter
Fridays in Skye 284
Refeshments 12:30–1pm
Talk 1–1:50pm
Organizers
Mandy Smith, President msmit055@ucr.edu 
Jonathan Alcaraz, Vice President jalca011@ucr.edu 
Alec Martin, Treasurer amart136@ucr.edu 
Noble Williamson, Secretary nwill024@ucr.edu 
Upcoming Talk
24 Jan 2020  Correspondence between Dominated Splitting and Spectrum of the Jacobi Operator 
Kateryna Alkorn  
We will talk about one of the basic results relating spectrum of Schrodinger operator and Uniform Hyperbolicity of the associated Schrodinger cocycle. After that we will proceed by extending the existing theory into a more general setting relating Dominated Splitting and Spectrum of Jacobi operator. We will talk about the problems we have encountered along the way and possible ways to resolve them. In the end we will see a proof of partial result from our hypothesis. 
Scheduled Talks
31 Jan 2020  Title TBD 
William Hoffer  
24 Jan 2020  Correspondence between Dominated Splitting and Spectrum of the Jacobi Operator 
Kateryna Alkorn  
We will talk about one of the basic results relating spectrum of Schrodinger operator and Uniform Hyperbolicity of the associated Schrodinger cocycle. After that we will proceed by extending the existing theory into a more general setting relating Dominated Splitting and Spectrum of Jacobi operator. We will talk about the problems we have encountered along the way and possible ways to resolve them. In the end we will see a proof of partial result from our hypothesis. 
17 Jan 2020  Upper bounds of the cop number 
Raymond Matson  
The game of cops and robbers is a type of graph searching problem where a team of cops try to capture a robber by moving onto the same vertex as the robber. The canonical question that arises is: what is the smallest number of cops needed to ensure that the cops will win for any graph of order 𝑛? Henri Meyniel conjectured that for any connected graph of order 𝑛, the number of cops needed is 𝑂(𝑛−−√). We will explore the upper bound of some specific graphs as well as attempts to prove Meyniel's conjecture. 
10 Jan 2020  An Introduction to Interval Bundles 
Jonathan Alcaraz  
Interval bundles are a way of taking a space we know and making it more topologically complicated while still maintaining homotopy type and hence maintaining the fundamental group. In lowdimensional topology, we see these when studying 3manifolds. It turns out that if a 3manifold smells like a surface (ie, its fundamental group is a surface group), then it is an interval bundle over a surface. 
Fall 2019
6 Dec 2019  Department Potluck! 
29 Nov 2019  No Meeting 
22 Nov 2019  On the Stability of SelfSimilar Blowup in Nonlinear Wave Equations 
Michael McNulty  
When studying nonlinear wave equations, one concerns themselves with the wellposedness of the Cauchy problem. Does a solution exist for some amount of time? Does it exist for all time? Is it unique? Does the solution depend continuously on the initial data? Within the context of energy supercritical wave equations, a typical way for solutions to fail to exist for all time is through the phenomenon of selfsimilar blowup. After making this observation, one is left pondering the stability of this blowup. In other words, one wants to know if there is an entire open set of initial data leading to this blowup. Answering this question for particular wave equations is an active area of research with lots of techniques stemming from wave maps. In this talk, we will discuss current work in progress toward establishing the asymptotic nonlinear stability of selfsimilar blowup in the strongfield Skyrme model. 
15 Nov 2019  Fractions, Continued: A Look at Continued Fractions 
Nick Newsome  
Continued fractions have been the subject of study for many years. A continued fraction is an expression that iteratively describes any real number. Rational numbers have a finite continued fraction representation, while irrationals have an infinite continued fraction representation. Continued fractions have applications ranging from approximating real numbers to solving Diophantine equations to (as I discovered recently) the study of differential equations. Although they are not incredibly difficult to comprehend, continued fractions are not typically part of the standard undergraduate (or graduate) mathematics curriculum. To that end, this talk will endeavor to introduce the basics of continued fractions in the hopes of showing how they can be used to do some pretty cool stuff. For example, have you ever considered just how irrational an irrational number can be? Continued fractions give us a way to develop a sort of hierarchy of irrationality. We will also (hopefully) show how continued fractions can be used to solve a particular Diophantine equation. 
8 Nov 2019  No Meeting 
1 Nov 2019  The Variable, Free and Bound 
Christian Williams  
In mathematics, computer science, and logic, one of the most useful ideas is also the most humble: the variable. But what exactly is a variable? When we write f(x)=x+3, how do we formalize the distinction between the "placeholder" x to be substituted, and the "real" value 3? Conventional algebra and logic do not answer this question; we simply take variables for granted. Though not widely known, the answer was given 25 years ago, in a paper called "Abstract Syntax with Variable Binding". This summer I got to visit the mathematician who realized this idea, and began to join in a grand project of laying the algebraic foundations of formal languages. Essentially, it is a new take on the ideas I presented last year: rather than thinking of algebraic theories as categories, one can think of them as functors T:C>Set, from a category of contexts to the category of sets  one interprets T(c) as the set of terms which can be derived from a context c (for simple languages, C=N, and a context "n" simply represents having n free variables). From this perspective, one can reformulate all of ordinary algebra; but this "category of presheaves" has a richer structure, in which we can say and do much more: in particular, we can formalize variables in a natural way. This is the key to having a universal language in which to express all of those we use in math and programming. Join me as we explore the beautiful world of "functors as languages", where we will connect such different concepts as the lambda calculus, species and simplicial sets, algebra and logic  there will even be integrals. Hope to see you there. 
25 Oct 2019  A Look at Microlocal Analysis 
Michael McNulty  
In the study of differential equations, one is always interested in studying equations of the form 𝑃𝑢=𝑓 where 𝑢 is some unknown function, 𝑓 is some known function, and 𝑃 is some differential operator. Typically, one hopes to solve for the unknown 𝑢 or to extract necessary properties of it. In other words, one wants to make sense of the righthand side of 𝑢=𝑃−1𝑓 or to know what spaces 𝑢 could live in. So, what does it mean to invert a differential operator? Where could the solution possibly live? Microlocal analysis provides a framework in which one can answer these questions. A good place to start the descent into microlocal analysis is with the study of pseudodifferential operators and how they propagate singularities. We will see how singularities of a distribution propagate along particular directions in the cotangent bundle which are determined uniquely by the pseudodifferential operator acting on them. 
18 Oct 2019  Finitely Additive Invariant Set Functions and Paradoxical Decompositions, or: How I Learned to Stop Worrying and Love the Axiom of Choice 
Adam D. Richardson  
This talk introduces the historic 𝜎additive measure problem in ℝ𝑛 and describes how the existence of nonmeasurable sets provided an answer to this problem that led mathematicians to explore the consequent finitely additive measure problem in ℝ𝑛. The Axiom of Choice plays an inextricable role in these problems. The existence of a finitely additive measure on 𝑆1 is developed carefully using results from functional analysis before the problem is explored in general. The application of the Axiom of Choice in these problems can yield paradoxical decompositions of subsets of ℝ𝑛 (and by extension ℝ𝑛 itself) such as the seminal Hausdorff halfthird paradox as well as the eponymous BanachTarski paradox. The development of these paradoxes is group theoretic in nature, and some of the group properties which yield such decompositions are discussed. This talk seeks to tell the mathematical origin story of such paradoxes, including detailing the Hausdorff halfthird paradox, while highlighting how the controversial Axiom of Choice led to these wholly counterintuitive yet absolutely fascinating measuretheoretic results. 
11 Oct 2019  Introduction to Operads 
Joe Moeller  
I'll give an intuitive introduction to the notion of "operad", a categorical tool for describing algebraic structures. Then we'll look at a few of the main examples that people use in homotopy theory and combinatorics. Time permitting, I'll also talk about the recognition principle and Kozsul duality. 
4 Oct 2019  A Crash Course on 𝑞Calculus 
Michael Pierce  
So 𝑞calculus, also called quantum calculus, by itself is just a "generalization" of arithmetic and calculus. However some arithmetic factoids in 𝑞calculus come up in representation theory and mathematical physics research. The goal of this talk though is to introduce 𝑞calculus as a standalone topic, and to familiarize the audience with some of those factoids so that it won't be too jarring to them if those factoids pop up in research. If time permits I'll also talk about current research being done into pure 𝑞calculus, and explain a bit about why that word generalization above is in quotes. 
27 Sep 2019  Interpreting Mathematics Rigorously 
Alexander Martin  
Rigor is the language of mathematics, but currently our languages are inherently not rigorous. It is possible for a student, using a pencil on paper with the notations and terms presented in the class, to make an error in a mathematical statement. I have been working on a project to develop a language which accounts for mathematical rigor. One major design goal is that assumptions, claims, and implication relations come from making a statement as opposed to from reading it, making it impossible to state something incorrect. The language is explicitly compiled by a computer so it makes sense to distinguish between valid statements and nonsense, nonsense being something which throws an error upon compilation. Any statement which can be stated (i.e. successfully compiled) is then tautologically true by design, so we will see how this works and what it means. Another goal is to be able to write new definitions, make new claims, and prove them in a way which a computer can understand and without modifying the language itself. This language involves interpreting mathematical statements as directed acyclic graphs, so we will see how that works. Statements are saved in XML files (like SVG and XHTML if you have ever seen those) and I have written a compiler in javascript (web browser). This talk is an overview of what I have developed so far, both the language itself and the tools to interact with it, and what I hope the future holds for the project. 
Mathematical Physics & Dynamical Systems
Weekly Seminars on Thursdays in Surge 268:
 FRG (Fractal Research Group) Seminar: 11:00 am 12:20 pm.
 MPDS (Mathematical Physics & Dynamical Systems) Seminar: 3:304:50 pm.
More detailed information (such as speakers, titles, abstracts & workshops) are available in the google calendar below.
Partial Differential Equations & Applied Math
PDE & AM Google Site
Winter 2020 Schedule

Jan 08 13:00 (Wed) Organizing meeting

Jan 15 13:00 (Wed) Dr. Xin Yang (Virginia Tech) (Zhang, Qi)

Jan 22 13:00 (Wed) Dr. Mykhailo Potomkin (UC Riverside)

Jan 29 13:00 (Wed) Dr. Mykhailo Potomkin (UC Riverside)

Feb 03 11:00 (Mon) Dr. Padmini Rangamani (UCSD) (Chen)

Feb 12 15:30 (Wed) Dr. Jingyi (Jessica) Li (UCLA) (Chen)

Feb 19 13:00 (Wed) Dr. Jasper Weinburd (Harvey Mudd College) (Cho)

Feb 21 11:00 (Fri) Dr. Sebastien Motsch (Arizona State University) (Cho)

Feb 26 13:00 (Wed) Dr. Dong Zhou (CSU LA) (Chen)

Mar 02 11:00 (Mon) Dr. Nan Hao (UCSD) (Chen)

Mar 04 13:00 (Wed) Dr. Derdei Bichara, (CSU Fullerton) (Chen)

Mar 06 11:00 (Fri) Dr. Dongwook Lee (UCSC) (Cho)

Mar 11 13:00 (Wed) Dr. Rodrigo Platte (Arizona State University) (Cho)