Calvin Fletcher

Date

Wednesday January 18, 2023
1:00 pm - 2:00 pm

Location

Jeffery Hall, Room 222 & Zoom

Curves Seminar

Wednesday, January 18th, 2023

Time: 1:00 p.m.  Place: Jeffery Hall, Room 222 & Zoom

Speaker: Calvin Fletcher

Title: Projective Toric Varieties

Abstract: We will provide a review of projective space, projective varieties and affine pieces. We will then introduce projective toric varieties and study some examples. We will also discuss the relationship between the affine cone of a projective toric variety arising from a finite set and the toric variety arising from that same finite set.

Sonja Ruzic

Date

Wednesday January 25, 2023
1:00 pm - 2:00 pm

Location

Jeffery Hall, Room 222 & Zoom

Curves Seminar

Wednesday, January 25th, 2023

Time: 1:00 p.m.  Place: Jeffery Hall, Room 222 & Zoom

Speaker: Sonja Ruzic

Title: Torus and Affine Pieces of Projective Toric Varieties

Abstract: We will continue our discussion of projective toric varieties. We will describe the torus of a projective toric variety by finding its character lattice. Next, we will describe its affine pieces. Time permitting, we will start the discussion on polytopes.

Benjamin Dozier (Cornell University)

Date

Friday January 27, 2023
2:30 pm - 3:30 pm

Location

Jeffery Hall, Room 234

Math & Stats Department Colloquium

Friday, January 27th, 2023

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

Speaker: Benjamin Dozier (Cornell University)

Title: Random hyperbolic surfaces and random regular graphs

Abstract: I will discuss the burgeoning field of random hyperbolic geometry. An important source of inspiration is the analogy between random hyperbolic surfaces and random regular graphs, rich objects which have been studied for many years. Both random objects tends to have good ``expansion properties'': mixing happens very quickly, they cannot be separated into big pieces by a cut of small length, and the Laplace operator has uniform spectral gap. I will end with some recent results on counting simple closed geodesics in both settings, joint with Jenya Sapir.

Nic Fellini (Queen's University)

Date

Monday January 23, 2023
4:30 pm - 5:30 pm

Location

Jeffery Hall, Room 319

Number Theory Seminar

Monday, January 23rd, 2023

Time: 4:30 p.m.  Place: Jeffery Hall, Room 319

Speaker: Nic Fellini (Queen's University)

Title: The bipartite sieve and applications to probabilistic Galois theory

Abstract: Given a monic polynomial f of degree n in Z[x], one can ask: what is the probability that the Galois group of f is a proper subgroup of the symmetric group on n symbols? This probabilistic Galois theory question has been studied for nearly 90 years! The most "satisfying" answer to this question is due to P. Gallagher in 1973. The key part of Gallagher's proof is the use of the multidimensional large sieve. The goal of this talk is to develop a much simpler sieve--- the bipartite sieve ---to study the probabilistic Galois theory question. Time permitting, we will discuss other applications of the bipartite sieve.

M. Ram Murty (Queen's University)

Date

Monday January 16, 2023
4:30 pm - 5:30 pm

Location

Jeffery Hall, Room 319

Number Theory Seminar

Monday, January 16th, 2023

Time: 4:30 p.m.  Place: Jeffery Hall, Room 319

Speaker: M. Ram Murty (Queen's University)

Title: SOME REMARKS ON HASSE'S INEQUALITY

Abstract: Hasse's inequality regarding the number of points on an elliptic curve mod p has a colorful history. Some of this is well-known in that it led to the rapid development of algebraic geometry. But some work of Davenport in the 1930's that predate Hasse's work is not so well-known. The beauty and elegance of this work got buried in the sands of time. I will give a streamlined version of both Davenport and Hasse's works and discuss especially what Davenport's work suggests for the classical Riemann hypothesis.

Somya Singh

Date

Wednesday January 25, 2023
12:00 pm - 1:00 pm

Location

Jeffery Hall, Room 319

Probability Seminar

Wednesday, January 25th, 2023

Time: 12:00 p.m.  Place: Jeffery Hall, Room 319

Speaker: Somya Singh

Title: Stochastic approximation: a dynamical systems viewpoint

Abstract: In this talk, we will see how Stochastic approximation is used to trace trajectories of a discrete random reinforcement process. We will look at the standard Stochastic approximation scheme and the main results which justifies the use of stochastic approximation to track the trajectories of discrete random reinforcement processes through an ordinary differential equation. We will also discuss the importance of assumptions that are used in constructing a stochastic approximation scheme.

Fangda Liu (University of Waterloo)

Date

Friday January 20, 2023
2:30 pm - 3:30 pm

Location

Jeffery Hall, Room 234

Math & Stats Department Colloquium

Friday, January 20th, 2023

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

Speaker: Fangda Liu (University of Waterloo)

Title: Model uncertainty and applications in insurance design

Abstract: The model uncertainty is of crucial importance when market participants are making risk management strategies. For a participant who adopts law-invariant risk measures for quantification, the study of the supremum of risk measure values can help the participant to better understand the performance of risk in the worst-case scenario. In this talk, we introduce several model uncertainty settings. The choices of risk measures, uncertainty sets, and transformations of the underlying risk play important roles in the characterization of the worst-case distribution. Motivated by the insurance policies, we mainly focus on stop-loss functions and limited loss functions. Furthermore, we discuss the optimal retention levels for participants in an insurance policy with model uncertainties.

Dr. Liu is an Assistant Professor in Actuarial Science at the Department of Statistics and Actuarial Science, University of Waterloo. Her research includes insurance/reinsurance design problems, characterization of risk measures, risk sharing and risk allocation problems, etc. Dr. Liu obtained her PhD in Actuarial Science from UW, and she is an associated fellow of the Society of Actuaries (SOA).

Noriko Yui (Queen's University)

Date

Friday January 13, 2023
2:30 pm - 3:30 pm

Location

Jeffery Hall, Room 234

Math & Stats Department Colloquium

Friday, January 13th, 2023

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

Speaker: Noriko Yui (Queen's University)

Title: Modularity of certain Calabi-Yau threefolds of Hodge type (1,1,1,1)

Abstract: We will focus on (families of) Calabi-Yau threefolds of Hodge type (1, 1, 1, 1), and discuss their modularity/automorphy in the framework of the Langlands Philosophy. In the last thirty years or so, we have witnessed tremendous advances on the modularity questions for Calabi-Yau varieties. Most of these results rest on the modularity of the two-dimensional Galois representations associated to them. The next simplest cases are those Calabi{Yau threefolds of Hodge type (1, 1, 1, 1). I will present modularity results on some examples of such Calabi{Yau threefolds (and motives).

Noriko Yui is a professor of mathematics at Queen's University in Kingston, Ontario.
A native of Japan, Yui obtained her B.S. from Tsuda College, and her Ph.D. in Mathematics from Rutgers University in 1974 under the supervision of Richard Bumby.
Known internationally, Yui has been a visiting researcher at the Max-Planck-Institute in Bonn a number of times and a Bye-Fellow at Newnham College, University of Cambridge. Her research is based in arithmetic geometry with applications to mathematical physics and notably mirror symmetry. Currently, much of her work is focused upon the modularity of Calabi-Yau threefolds. Notably, she and Fernando Q. Gouvea have shown that for X, a projective rigid Calabi-Yau threefold defined over the rationals , the L-function of X is the L-function of a certain modular form.
Professor Yui has been the managing editor for the journal Communications in Number Theory and Physics since its inception in 2007. In 2022 she became a fellow of the Canadian Mathematical Society.

Nima Hoda (Cornell University)

Date

Monday January 9, 2023
4:30 pm - 5:30 pm

Location

TBA

Algebra & Geometry Seminar

Monday, January 9th, 2023

Time: 4:30 p.m.  Place: TBA

Speaker: Nima Hoda (Cornell University)

Title: Strong shortcut groups and asymptotic cones

Abstract:

Website details here: https://mast.queensu.ca/~georep/Fall%20'22.html

Monica Garcis (Paris-Saclay University)

Date

Monday December 12, 2022
4:30 pm - 5:30 pm

Location

TBA

Algebra & Geometry Seminar

Monday, December 12th, 2022

Time: 4:30 p.m.  Place: TBA

Speaker: Monica Garcis (Paris-Saclay University)

Title: Towards stability for projective presentation

Abstract:

Website details here: https://mast.queensu.ca/~georep/Fall%20'22.html