## Math Department Seminar Information

**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.

##### Operator Algebras & Related Topics - Dr. Feng Xu - 3:00 - 3:50 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. Mei-Chu 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.

#### Thursdays

##### Fractal Geometry, Complex Dimension & Zeta Functions - Dr. Michel Lapidus - 9:30 - 10:50 a.m.

##### Fractal Research Group - Dr. Michel Lapidus - 11:00 a.m. - 12:20 p.m.

##### Lie Theory - Dr. Vyjayanthi Chari - 12:30 - 1:50 p.m.

##### Mathematical Physics & Dynamical Systems - Dr. Michel Lapidus - 3:30 - 4:50 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 schedules are provided by their respective coordinators. Not all seminars have extended or current schedules available.

##### Algebraic Geometry

##### Fall 2020

https://math.ucr.edu/~joselg/agseminar

Date |
Speaker |
Title |
Abstract |

Tuesday, October 13, 2020 Start: 11:00 AM Location: Online via Zoom (Please email the organizers if interested.) |
Patricio GallardoUC Riverside |
On wonderful blow-ups. | Techniques for constructing good compactifications of an open set is one of the main problems within Algebraic Geometry. In this talk, I will describe a tool known as Wonderful Compactifications due to Li-Li which generalizes earlier work by De Concini-Procesi on hyperplane arrangements. Applications to moduli problems will be described as well. |

Tuesday, October 20, 2020 Start: 11:00 AM Location: Online via Zoom (Please email the organizers if interested.) |
Patricio GallardoUC Riverside |
On wonderful blow-ups (second part). | We will continue describing the theory of wonderful blow-ups. A particular focus is given to applications within moduli theory as well as open problems. |

Tuesday, October 27, 2020 Start: 11:00 AM Location: Online via Zoom (Please email the organizers if interested.) |
Benjamin SchmidtLeibniz Universität Hannover |
A curious moduli space on cubic threefolds. | The intermediate Jacobian J(X) of a cubic threefold X was introduced by Clemens and Griffiths in 1972 to prove irrationality of cubic threefolds. It is an abelian variety that can be thought of as parametrizing degree zero cycles in dimension one up to rational equivalence. In this talk we will concentrate on its theta divisor ϴ. Clemens and Griffiths proved the so-called Torelli theorem for cubic threefolds that says that the pair (J(X),ϴ) determines the cubic threefold. Shortly after, Mumford pointed out that X can be recovered just from the singularities of the theta divisor. In fact, it has a unique singularity whose tangent cone is the affine cone of the cubic X. Blowing the singularity up yields a resolution of singularities. We will construct this resolution as a moduli space of rank three vector bundles. This allows us to recover the so-called derived Torelli theorem. It roughly says that a certain triangulated subcategory (called the Kuznetsov component of X) of the bounded derived category of coherent sheaves determines X. |

Tuesday, November 3, 2020 Start: 11:00 AM Location: Online via Zoom (Please email the organizers if interested.) |
US Election Day |
Election Day. | No seminar meeting on US Election Day. |

Tuesday, November 10, 2020 Start: 11:00 AM Location: Online via Zoom (Please email the organizers if interested.) |
Olivia DumitrescuUniversity of North Carolina at Chapel Hill |
TBA | TBA |

Tuesday, November 17, 2020 Start: 11:00 AM Location: Online via Zoom (Please email the organizers if interested.) |
Dagan KarpHarvey Mudd College |
TBA | TBA |

Tuesday, November 24, 2020 Start: 11:00 AM Location: Online via Zoom (Please email the organizers if interested.) |
Antonio Laface.University of Concepcion |
TBA | TBA |

Tuesday, December 1, 2020 Start: 11:00 AM Location: Online via Zoom (Please email the organizers if interested.) |
Javier Gonzalez-AnayaUC Riverside |
TBA | TBA |

Tuesday, December 8, 2020 Start: 11:00 AM Location: Online via Zoom (Please email the organizers if interested.) |
Bernt Ivar Utstøl NødlandNorwegian Defence Research Establishment |
TBA | TBA |

##### Category Theory

https://sites.google.com/ucr.edu/ucrcategoryseminar/home

###### Fall 2020 UC Riverside seminar for **Category Theory and Applications**

**Organizers** Joe Moeller, Jade Master, Christian Williams **Advisor** John Baez

**Schedule** (not determined, still flexible)

10/12 JC **Symmetric monoidal closed categories**

10/19 Jade **The algebraic path problem**

10/26 Sarah **Equivariant homotopy theory**

11/02 David **Double categories and open systems**

11/09 John **Categorifying the natural numbers**

11/16 Chris **Logic of cartesian closed categories**

11/23 Christian **co/Monads**

11/30 Joe **Schur functors**

12/07 Todd **Topos Theory**

##### Commutative Algebra

https://eloisagrifo.github.io/UCRseminar.html

#### Fall 2020 schedule

- October 2, 2020

Organizational meeting

- October 9, 2020

Eloísa Grifo (UCR)

What is Commutative Algebra and what will this seminar be about?

- October 16, 2020

Eloísa Grifo (UCR)

Betti numbers and free resolutions

Abstract: A (minimal) free resolution of a finitely generated module M describes its generators, relations, the relations among the relations, etc, and contains lots of geometric and algebraic information about a module. In this talk, we will give a friendly introduction to free resolutions and construct several examples.

- October 23, 2020

Adam Boocher (University of San Diego)

TBA

- October 30, 2020

Alessandra Costantini (UCR)

Combinatorial Commutative Algebra I

- November 6, 2020

Alessandra Costantini (UCR)

Combinatorial Commutative Algebra II

- November 13, 2020

Eloísa Grifo (UCR)

TBA

- November 20, 2020

Jack Jeffries (University of Nebraska-Lincoln)

TBA

- December 4, 2020

Benjamin Briggs (University of Utah)

The friendship between commutative algebra and rational homotopy theory

##### Differential Geometry

##### The Schedule for the Fall of 2020, Fridays 11--11:50AM, starting on Oct. 3.

###### Email fred "at" math.ucr.edu for the zoom link

##### 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: 3:30-4:50 pm.

More detailed information (such as speakers, titles, abstracts & workshops) are available in the google calendar below.

##### Ergodic Theory & Spectral Theory

##### Graduate Student Seminar

##### Fall 2020 TBP

##### Lie Theory

https://sites.google.com/view/petersamuelson/lie-theory-seminar

##### Lie Theory

This is the (minimal) website for the Lie Theory Seminar at UCR for the Fall 2020 quarter, which is organized by Vyjayanthi Chari. Please contact Peter Samuelson for questions or comments.

###### Speakers

October 6: Wee Liang Gan, UCR.

October 13: Wee Liang Gan, UCR.

October 20: Pablo Ocal, Texas A&M.

October 27: Peter Samuelson, UCR.

November 3: Peter Samuelson, UCR.

November 10:

November 17:

November 24:

December 1:

December 8:

###### Titles and Abstracts

**October 6:** Wee Liang Gan FI-modules: Proof of Representation Stability

Abstract: I will explain the notion of representation stability and the proof that finitely generated FI-modules are representation stable.

**October 13**: Wee Liang Gan FI-modules: Proof of Noetherianity

Abstract: I will explain the proof that finitely generated FI-modules over a noetherian ring are noetherian.

**October 20**: Pablo Ocal, Hochschild cohomology of general twisted tensor products

Abstract: The Hochschild cohomology is a tool for studying associative algebras that has a lot of structure: it is a Gerstenhaber algebra. This structure is useful because of its applications in deformation and representation theory, and recently in quantum symmetries. Unfortunately, computing it remains a notoriously difficult task. In this talk we will present techniques that give explicit formulas of the Gerstenhaber algebra structure for general twisted tensor product algebras. This will include an unpretentious introduction to this cohomology and to our objects of interest, as well as the unexpected generality of the techniques. This is joint work with Tekin Karadag, Dustin McPhate, Tolulope Oke, and Sarah Witherspoon.

##### 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: 3:30-4:50 pm.

More detailed information (such as speakers, titles, abstracts & workshops) are available in the google calendar below.

##### Partial Differential Equations & Applied Math

##### Fall 2020 Schedule

https://sites.google.com/ucr.edu/ucriverside-math-ampde-seminar/

Oct 07 10:00 (Wed) Organizing Meeting

Oct 14 10:00 (Wed) Dr. Jia Gou (UC Riverside) (Gou)

Oct 21 10:00 (Wed) Dr. Zheng Chen (University of Massachusetts) (Chen)

Oct 28 10:00 (Wed) Dr. Wing Tat Leung (University of California, Irvine) (Chow)

Nov 04 10:00 (Wed) Dr. Michael Lindstrom (University of California, Los Angeles) (Gou)

Nov 11 10:00 (Wed) Dr. Huan Lei (Michigan State University) (Cho)

Nov 18 10:00 (Wed) Dr. Levon Nurbekyan (University of California, Los Angeles) (Chow)

Nov 25 10:00 (Wed) Dr. Qiliang Wu (Ohio University) (Chen)

Dec 02 10:00 (Wed) Dr. Ali Pakzad (Indiana University) (Chow)

Dec 09 10:00 (Wed)

##### Topology

https://sites.google.com/view/ucrtopologyseminar/home

Wednesday October 7, 12:00-12:50, Zoom

Title: Mapping class groups, multiple Kodaira fibrations, and CAT(0) spaces.

Abstract: A Kodaira fibration is a compact complex surface endowed with a holomorphic submersion onto a Riemann surface, which has connected fibers and is not isotrival. Using a classical construction due to Atiyah and Kodaira, we prove that the mapping class group of a once punctured genus g surface embeds into the mapping class group of a closed surface of larger genus. We also discuss questions related to the existence of CAT(0) metrics on Kodaira fibrations or to the number of distinct fiberings of such complex surfaces. This is based on a joint work with Claudio Llosa Isenrich (arXiv:2001.03694).

Wednesday October 21, 12:00-12:50, Zoom

Title: Congruence RFRS towers

Abstract: Ian Agol introduced the concept of a RFRS (residually finite rational solvable) tower, a purely group theoretic condition, in showing certain hyperbolic 3-manifolds virtually fiber over the circle. I will talk about joint work with Agol where we develop general tools one can use to find RFRS towers consisting of congruence subgroups of certain arithmetically defined groups. We will then apply these tools to show that many arithmetic hyperbolic 3-manifolds virtually fiber on a congruence subgroup and to answer a question of Friedl and Vidussi.

Wednesday November 4, 12:00-12:50, Zoom

Corey Bregman (University of Southern Maine)

Title: TBA

Abstract: TBA

Wednesday November 18, 12:00-12:50, Zoom

Title: TBA

Abstract: TBA

Wednesday November 25, 12:00-12:50, Zoom

Title: TBA

Abstract: TBA

Wednesday December 2, 12:00-12:50, Zoom

Asaf Hadari (University of Hawai'i at Manoa)

Title: Mapping class groups in genus at least 3 do not virtually surject to the integers.

Abstract: Mapping class groups of surfaces of genus at least 3 are perfect, but their finite-index subgroups need not be - they can have non-trivial abelianizations. A well-known conjecture of Ivanov states that a finite-index subgroup of a mapping class group in genus at least 3 has finite abelianization. We will discuss a proof of this conjecture, which goes through an equivalent representation-theoretic form of the conjecture due to Putman and Wieland.