Those pictures appearing on my welcome page? They all appear below… enjoy!
Longer Mathematical Pieces 


Two stories from the theory of words


The combinatorics of pointed Hopf algebras


Hopf structures on the multiplihedra



Littlewood–Richardson rules from Hopf algebras


Revisiting Markoff's study of quadratic forms



Finding primitives via transfer of structure


A stable basis for QSym over Sym



Lagrange’s theorem for Species


Where was Aaron? 


Hint:
on an island in the Isar


Hint:
google Buren



Hint:
near Týn Church


Hint:
you’ll have to ask me, it has vanished


Hint:
not a boathouse, but a boathouse


Hint:
near Chamonix–Mont Blanc


Hint:
on the “Ring Road”


