# Seminars and colloquia

E.g., Jan. 29, 2022

### Farid Aliniaeifard

UBC
Modular relations between chromatic symmetric functions

February 1, 2022

Zoom - https://ubc.zoom.us/j/62676242229?pwd=RURtUC9UYXEweVZTMTNGT1EvY1FLZz09

In 1995, Stanley introduced the chromatic symmetric functions. The study of chromatic symmetric functions of graphs inspired two main research directions. The first research direction is to prove the Stanley-Stembridge conjecture: if a poset is $(3+1)$-free, then the chromatic ... Read more
• Discrete mathematics

### Hemanshu Kaul

Illinois Institute of Technology
Chromatic polynomial and counting DP-colorings of graphs : Problems and progress

February 8, 2022

Zoom - https://ubc.zoom.us/j/62676242229?pwd=RURtUC9UYXEweVZTMTNGT1EvY1FLZz09

In 1912, Birkhoff, introduced the chromatic polynomial of a graph G that counts the number of proper colorings of G. List coloring, introduced in the 1970s by Erdos among others, is a natural generalization of ordinary coloring where each vertex has a restricted list of colors ... Read more
• Discrete mathematics

### Colin Defant

Princeton University
Variants of pop-stack sorting

February 15, 2022

Zoom - https://ubc.zoom.us/j/62676242229?pwd=RURtUC9UYXEweVZTMTNGT1EvY1FLZz09

The purpose of this talk is to advertise noninvertible combinatorial dynamics, a largely unexplored area with several interesting directions. We will focus on the pop-stack sorting map, a specific noninvertible operator on the symmetric group, along with several of its ... Read more
• Discrete mathematics

### Manik Dhar

Princeton
The Kakeya Set conjecture over Z mod N for general N

February 22, 2022

Zoom - https://ubc.zoom.us/j/62676242229?pwd=RURtUC9UYXEweVZTMTNGT1EvY1FLZz09

A Kakeya Set in (Z/N Z)^n is a set that contains a line in every direction. It has been known for over a decade that such sets must be large when N is prime (or more generally over any finite field). This goes back to Dvir's proof of the finite field Kakeya conjecture as posed ... Read more
• Discrete mathematics

### Brandon Hanson

University of Maine
TBA

March 1, 2022

Zoom - https://ubc.zoom.us/j/62676242229?pwd=RURtUC9UYXEweVZTMTNGT1EvY1FLZz09

• Discrete mathematics

### Sergi Elizalde

Dartmouth College
Rowmotion on 321-avoiding permutations

March 8, 2022

Zoom - https://ubc.zoom.us/j/62676242229?pwd=RURtUC9UYXEweVZTMTNGT1EvY1FLZz09

We give a natural definition of rowmotion for 321-avoiding permutations, by translating, through bijections involving Dyck paths and the Lalanne-Kreweras involution, the analogous notion for antichains of the positive root poset of type A. We prove that some permutation ... Read more
• Discrete mathematics

### Michael Simkin

Harvard University
The number of n-queens configurations

March 22, 2022

Zoom - https://ubc.zoom.us/j/62676242229?pwd=RURtUC9UYXEweVZTMTNGT1EvY1FLZz09

The n-queens problem is to determine Q(n), the number of ways to place n mutually non-threatening queens on an n x n board. We show that there exists a constant 1.94 < a < 1.9449 such that Q(n) = ((1 + o(1))ne^(-a))^n. The constant a is characterized as the solution to a ... Read more
• Discrete mathematics

### Sergey Goryainov

Hebei Normal University and Chelyabinsk State University
On two types of cliques related to eigenspaces of strongly regular graphs

April 5, 2022

Zoom - https://ubc.zoom.us/j/62676242229?pwd=RURtUC9UYXEweVZTMTNGT1EvY1FLZz09

We consider graphs without loops and multiple edges. A $k$-regular graph with $n$ vertices is called a strongly regular graph with parameters $(n,k,a,c)$ if any two adjacent vertices have exactly $a$ common neighbours and any two distinct non-adjacent vertices have $c$ common ... Read more
• Discrete mathematics