Having lunch in a Garden of Eden

Today I talked about the Garden-of-Eden theorem, the first rigorous result in cellular automata theory.

I wrote a post about it in my new blog, dedicated to cellular automata, which I launched this week. The post contains extended proofs and examples, and most important, fixes several errors I had made during the talk. I might update it later, by adding figures—which are well known to take their time.

Link: http://anotherblogonca.wordpress.com/2013/06/27/in-a-garden-of-eden/

An initial solution to the monad problem, and then some more

This is the second of two talks about monads, based on the very good notes by Andrea Schalk and continuing the one I gave on the 30th of May. Recall that we are trying to solve the following problem:

given a monad T = (T, \eta, \mu), find an adjunction (F, G, \eta, \varepsilon) such that T = GF and \mu = G \varepsilon_F

If the adjunction (F, G, \eta, \varepsilon) solves the problem above, we say that it generates the monad T.

The first solution to this problem was given by the Swiss mathematician Heinrich Kleisli, and is based on an alternative way of defining monads, as it is the case with adjunctions. Continue reading