Dear all, as some of you know, Frederic Chapoton has given a talk on operads at the SLC in Lyon. I'll just give a (very, very) short account on the connection to species here. His slides are available online:
http://math.univ-lyon1.fr/~chapoton/ ------------------------------------------------------------------------------- A symmetric operad is a species P together with a morphism gamma: P o P -> P, where o is the (usual) composition of (ordinary) species. To add a little confusion, gamma is also called "composition" or "product"... gamma can be decomposed into "simple compositions" o_i : P(I u {i}) x P(J) -> P(I u J) A non-symmetric operad is the same thing in the world of linear species. ------------------------------------------------------------------------------- Operads seem to become interesting when one gives them a group structure. But, in fact, that's my biggest problem with operads: I do not see yet, how I could use them. ------------------------------------------------------------------------------- Apart from this, Frederic asked for an implementation of the inverse of the substitution (of species)... Of course, the result is then a virtual species, but at least there is a formula in BLL. And, he confirmed that vectorial species, i.e., functors (finite) Set -> (finite dimensional) Vector Spaces would be more interesting... All the best, Martin ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Aldor-combinat-devel mailing list Aldor-combinat-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/aldor-combinat-devel
