rybu's blog

Why I am no longer a member of the CMS

About a year ago I let my membership to the CMS (Canadian Mathematics Society) lapse.   This has not come easily for me.  It is my hope that Canadian mathematicians have an effective and engaged society.  But I feel the CMS has done too little for Canadian mathematics in relation to its economic burden, and has lost its way.

Cascade Topology Seminar, Spring 2015

The canonical Seifert surface argument

One of the earliest "proper" obstruction-theory arguments in topology goes back to Bruschlinsky, Math. Ann. 109 (1934), stating that the homotopy-classes of maps from a space to the circle are in one-to-one correspondence with the 1-dimensional cohomology of the space. 

[X,S1] = H1(X)

The view from inside a mirrored tetrahedron.

What would it look like being inside a regular tetrahedron, but with all the walls made from mirrors?   Glad you asked. 

Here is a little movie of the above scene:

Canada is seeded with topologists

Canada has reached a little threshold for topologist-density recently.  Every province except PEI has a topologist in either a permanent position or a tenure-track job. As far as I know this is unprecedented. 

BC: Rolfsen, Adem, Pettet, Ben Williams, myself.

Alberta: Bauer, Zvengrowski, Peschke. 

Saskatchewan: Stanley. 

Manitoba: Adam Clay. (this is recent news to me!)

Some videos of me

Two videos of me. The first has plenty of editing to cut out my prolific usage of "uh". It's a general description of topology, intended for inquisitive non-experts.

Milnor's interchange symmetry argument

I'm teaching a differential geometry course this semester and having fun with it. This is kind of over-the-top use of computer graphics, but...

A small compilation of topology videos

Recently a bunch of nice classic topology videos have been appearing in various locations. I thought I'd put together a little list of some of them.

Most common small 3-manifolds in the 4-sphere

I've been enumerating vertex-normal 3-manifolds in triangulated homotopy 4-spheres recently. I thought I'd put a list of the most commonly found 3-manifolds somewhere. This seems like a good a place as any.


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