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2023 H.N. Gupta Memorial Lecture

Thu., May. 4, 2023 2:00 p.m.

Location: Live Stream

This is the annual lecture in memory of Dr. H.N. Gupta, Professor Emeritus.

Speaker:  Claude Laflamme, University of Calgary

Title:  How many siblings do you have?

... with a good lesson in mathematical writing!

Zoom Link: 


Two structures are called siblings, or equimorphic, if each embeds in the other.

Siblings need not be isomorphic and the main mathematical objective is to describe these equimorphic structures. A first step is simply the ability to count them (up to isomorphy), the so-called sibling number.

Some early 2000 conjectures stated that the sibling number jumped to infinity as soon a single non-isomorphic sibling was found, and we will review various developments in those directions over the years.

On the hand by chance and to our surprise, we learned that a 2008 thesis claimed a counterexample to one of those conjectures. We will argue that mathematical writing was the root cause of this claim not being verified until now, and how it eventually triggered powerful counterexamples for several conjectures.


Lecture Poster (53 kB) PDF File