# Duncan McCoy (UQAM)

Date

Friday September 16, 20222:30 pm - 3:30 pm

Location

Jeffery Hall, Room 234## Math & Stats Department Colloquium

**Friday, September 16th, 2022**

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

**Speaker:** Duncan McCoy (UQAM)

**Title:** The unknotting number

**Abstract:** This talk will be a gentle introduction to the unknotting number. A mathematical knot is a tangled up circle in 3-dimensional space -- think of your shoe laces but with the ends fused together. The unknotting number of a knot is the minimum number of times the knot must be passed through each other in order to transform it into a standard round circle (the 'unknot'). Despite its simple definition, the unknotting number is in general very hard to compute. I will discuss some examples and explain a little of what is known and unknown about the unknotting number.