This is the discussion board for Federico Ardila’s 2012 class in Hopf algebras and combinatorics. The purpose of this blog is to actively discuss the topics as we study them, and exchange ideas that may lead to a better understanding of the material, as well as research projects.

No idea is bad here. No question is stupid here. Half-baked thoughts are very welcome.

The discussions will be in english. If your english is not very good, it can get better here. Don’t be shy.



  1. HW 3 Problem 3(a)

    For problem 3(a) \displaystyle \sum_{(h)}h_{(1)} S(h_{(2)}) \otimes h_{3} = h can we replace \displaystyle \sum_{(h)}h_{(1)}S(h_{2}) with \epsilon(h)1? Or is this not valid because h_{(3)} is inside the sum?

    Thank you in advance!!


  2. alabair

    Thank very much. I have an highlithing idea for abstract concept like the Hopf algebra when I watch the videos avalable in this web site: https://www.youtube.com/playlist?list=PL-XzhVrXIVeRLeezwY9h4M68k6yB3yOo-
    What about the shuffle product symbol in order to understand some paper on rough paths theory?

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