Sonja Ruzic

Date

Thursday March 7, 2024
4:00 pm - 5:00 pm

Location

Jeffery Hall, Room 319

Curves Seminar

Thursday, March 7th, 2024

Time: 4:00 p.m.  Place: Jeffery Hall, Room 319

Speaker: Sonja Ruzic

Title: Commutative rings with a cluster algebra structure.

Abstract: In this talk, we look at several examples of commutative rings which have an inherent cluster algebra structure. In particular, we will see different explicit examples of commutative rings which are also cluster algebras of finite type.

Yanglei Song (Queen's University)

Date

Thursday March 7, 2024
5:30 pm - 6:30 pm

Location

Jeffery Hall, Room 118

Math Club

Thursday, March 7th, 2024

Time: 5:30 p.m.  Place: Jeffery Hall, Room 118

Speaker: Yanglei Song (Queen's University)

Title: Stein's Paradox, Lemma, and Method

Abstract: Consider the estimation of three unrelated quantities, such as the speed of light, your daily coffee consumption, and Kingston's COVID activity level. The James–Stein estimator proposes to estimate them simultaneously and borrow information across them. For normally distributed data, it beats, in terms of the sum of quadratic losses, the most natural approach, which estimates each quantity individually. We prove this counter-intuitive result using Stein's lemma.

The reverse direction of Stein's lemma characterizes the standard normal distribution, It motivates a family of powerful techniques now called Stein's method for bounding distances between probability distributions. We discuss the basic idea behind the method.

 

Wei Tu (Queen's University)

Date

Friday March 8, 2024
2:30 pm - 3:30 pm

Location

Jeffery Hall, Room 234

Math & Stats Department Colloquium

Friday, March 8, 2024

Time: 2:30 p.m.  Place: Jeffery Hall, Room 234

Speaker: Wei Tu (Queen's University)

Title: Informative Censoring in Oncology Clinical Trials

Abstract: Clinical trials remain the cornerstone for evaluating new cancer treatments, with the selection of primary endpoints being crucial to the trial’s design and potential to change medical practice. Progression-free survival (PFS) is frequently chosen as an endpoint in oncology trials due to the advantage of shorter study durations, particularly in studies of early-stage diseases. Nevertheless, informative censoring presents a challenge in trials that use PFS as the primary endpoint. This type of censoring occurs when the projected outcomes for individuals who leave the study early differ from those who continue, which can skew the trial’s findings. In this talk, I will discuss the consequences of informative censoring and the statistical methods used to mitigate its effects, using data from the Canadian Cancer Trials Group (CCTG) MA.17R trial as an example. To assess informative censoring’s effect on estimated treatment benefits, we evaluate the use of competing risk assessments and gamma imputation methods for handling non-breast cancer mortality within the dataset. Moreover, we utilize inverse probability censoring weighting (IPCW) to mitigate its impact, assigning weights to participants based on shared characteristics to accurately represent those lost to on-breast cancer causes.

Bio: Dr. Tu is a Senior Biostatistician with the Canadian Cancer Trials Group and an Assistant Professor in the Department of Public Health Sciences at ºÚÁϳԹÏ×ÊÔ´. He completed both his MSc and PhD in Statistics at the University of Alberta. His research interests encompass clinical trial design and analysis, statistical machine learning, data privacy, and genomic data science. His work is supported by the Natural Sciences and Engineering Research Council of Canada, Canadian Institutes of Health Research and Canadian Cancer Society.

 

Sunil Naik (Queen's University)

Date

Monday March 4, 2024
2:30 pm - 3:30 pm

Location

Jeffery Hall, Room 202

Number Theory Seminar

Monday, March 4th, 2024

Time: 2:30 p.m.  Place: Jeffery Hall, Room 202

Speaker: Sunil Naik (Queen's University)

Title: A note on Dowling lattices

Abstract: In this talk, we will discuss the general framework of sieve methods for geometric lattices. The special case of Dowling lattices leads us to certain sums involving Whitney numbers of these lattices, which we will estimate using tools from complex analysis. This is an ongoing joint work with Prof. M. Ram Murty.

Ugo Piomelli (ºÚÁϳԹÏ×ÊÔ´)

Date

Tuesday March 5, 2024
9:30 am - 10:30 am

Location

Jeffery Hall, Room 319 (Via Zoom)

PDEs & Applications Seminar

Tuesday, March 5th, 2024

Time: 9:30 a.m.  Place: Jeffery Hall, Room 319 (Via Zoom)

Speaker: Ugo Piomelli (ºÚÁϳԹÏ×ÊÔ´)

Title: Numerical simultions of turbulence

Abstract: Turbulence has been described as the last unsolved problem of classical mechanics. It is a phenomenon that affects most fluid flows in engineering and the natural sciences, and its understanding is crucial to improve the design of ship, aircraft, and cars, the prediction of weather patterns, or the impact of environmental changes. Turbulence is a multiscale phenomenon, and is neither entirely deterministic, nor completely stochastic. While statistical mechanics tools can be used to predict the behaviour of the small and intermediate-sized motions, no theory has fully explained the behaviour of the larger ones, which depend strongly on the boundary conditions. Yet, it is the larger scales that drive the momentum and energy transport.

The numerical solution of the equations of motion, the Navier-Stokes equations, is a viable alternative to theory; however, the computational resources required for simulations of complex flows have been a limiting factor. The increased availability of computational resources and the development of new algorithms has made it possible, in recent years, to approach more realistic problem. High-fidelity simulations have resulted in better understanding of the physics, and, in turn, in the development of more accurate lower-level models for industrial design.

In this talk the challenges associated with the simulation of turbulent flows will be discussed. The most common numerical methods will be presented, with their advantages and disadvantages. A series of illustrative examples from Piomelli's research group will then be presented.

(Short) Bio: Ugo Piomelli obtained a Laurea in Ingegneria Aeronautica from the Università di Napoli "Federico II" in 1979. He then earned a Master of Science Degree in Aerospace Engineering from the University of Notre Dame in 1984 and a PhD in Mechanical Engineering from Stanford University in 1988. From 1987 to 2008 he was on the faculty of the Department of Mechanical Engineering at the University of Maryland, first as Assistant, then Associate and finally Full Professor. He served as Associate Chair and Director of Graduate studies from 2002 to 2007. In August 2008 he joined the Department of Mechanical and Materials Engineering at ºÚÁϳԹÏ×ÊÔ´ in Kingston, Ontario, where he held, from 2008 to 2022, the Tier 1 Canada Research Chair in Turbulence Simulation and Modelling.

Professor Piomelli has published over 100 refereed journal articles in the fields of turbulence and transition modelling and simulation. His work has been cited over 24,400 times, and he has an h-index of 55 (Google Scholar). He was elected Fellow of the Royal Society of Canada in 2015, of the Canadian Academy of Engineering in 2021, of the American Society of Mechanical Engineers in 2009, of the Institute of Physics (UK) in 2004 and of the American Physical Society in 2002. Since 2015, he has been the Editor-in-Chief of the Journal of Turbulence. His present research includes studies of the flow in rivers and lakes, turbulent boundary layers over smooth and rough surfaces, model development for large-eddy simulations, and flows in hydro-electric turbines and aeronautical applications.

Deepanshu Prasad

Date

Thursday February 29, 2024
4:00 pm - 5:00 pm

Location

Jeffery Hall, Room 319

Curves Seminar

Thursday, February 29th, 2024

Time: 4:00 p.m.  Place: Jeffery Hall, Room 319

Speaker: Deepanshu Prasad

Title: Seed Patterns of Type B_n and C_n are of Finite Type.

Abstract: We'll finish our discussion on folding and use the folding technique to prove that seed patterns, or the associated cluster algebra, of type B_n and C_n are of finite type.

Ivan Dimitrov (Queen's University)

Date

Thursday February 29, 2024
5:30 pm - 6:30 pm

Location

Jeffery Hall, Room 118

Math Club

Thursday, February 29th, 2024

Time: 5:30 p.m.  Place: Jeffery Hall, Room 118

Speaker: Ivan Dimitrov (Queen's University)

Title: Proof of the sensitivity conjecture

Abstract: IIn 2019 Hao Huang proved that, if $P$ is a set of $2^{n−1} + 1$ vertices of an $n$-dimensional cube, it contains a vertex with at least $\sqrt{n}$ neighbours in $P$.

This settled the nearly 30-year-old Sensitivity Conjecture.

We will discuss the conjecture, and see Huang’s proof.

Brian Hall (University of Notre Dame)

Date

Friday March 1, 2024
2:30 pm - 3:30 pm

Location

Jeffery Hall, Room 234

Math & Stats Department Colloquium

Friday, March 1st, 2023

Time: 2:30 p.m.  Place: Jeffery Hall, Room 234

Speaker: Brian Hall (University of Notre Dame)

Title: Heat flow on polynomials with connections to random matrix theory

Abstract: Here is a simple question with a surprisingly rich answer: How do the roots of a polynomial change as the polynomial evolves according to the heat equation? The simplest case of this question concerns the backward heat flow on polynomials with all real roots. In this case, an old theorem of P´olya and Benz says that the roots will remain real. Much more recent results tell us how these real roots evolve in the high-degree limit—and there is a surprising connection to random matrix theory. Things become even more interesting when we study the heat flow (forward or backward) on polynomials with complex roots. I will present some recent conjectures and rigorous results on this question. This is joint work with Ching Wei Ho, Jonas Jalowy, and Zakhar Kabluchko. The talk will be self-contained and have lots of pictures and animations.

Bio: Brian Hall received his Ph.D. from Cornell University in 1993 under Leonard Gross and is currently a professor at the University of Notre Dame. He is the author of two textbooks in the Graduate Texts in Mathematics series, Quantum Theory for Mathematicians and Lie Groups, Lie Algebras and Representations. His recent interests concern random matrices, random polynomials, and free probability.

 

Nicola de Nitti (EPFL)

Date

Tuesday February 13, 2024
9:30 am - 10:30 am

Location

Jeffery Hall, Room 319 (Via Zoom)

PDEs & Applications Seminar

Tuesday, February 13th, 2024

Time: 9:30 a.m.  Place: Jeffery Hall, Room 319 (Via Zoom)

Speaker: Nicola de Nitti (EPFL)

Title: Sharp bounds on enstrophy growth for viscous scalar conservation laws

Abstract: We prove sharp bounds on the enstrophy growth in viscous scalar conservation laws. The upper bound is, up to a prefactor, the enstrophy created by the steepest viscous shock admissible by the $L^\infty$ and total variation bounds and viscosity. This answers a conjecture by D. Ayala and B. Protas (Physica D, 2011), based on numerical evidence, for the viscous Burgers equation. This talk is based on a joint work with D. Albritton [].

Agnid Banerjee (ASU)

Date

Tuesday February 27, 2024
9:30 am - 10:30 am

Location

Jeffery Hall, Room 319 (Via Zoom)

PDEs & Applications Seminar

Tuesday, February 27th, 2024

Time: 9:30 a.m.  Place: Jeffery Hall, Room 319 (Via Zoom)

Speaker: Agnid Banerjee (ASU)

Title: Space like strong unique continuation for some fractional parabolic equations

Abstract: My lecture will focus on a very classical subject: when do the zeros of a solution to a PDE spread? I will start with a brief historic overview. Then I will talk on some recent work of mine on space like strong unique continuation for fractional heat type equations which is joint with Vedansh Arya, Donatella Danielli and Nicola Garofalo.