most recent 30 from http://mathoverflow.net 2013-05-21T21:27:49Z http://mathoverflow.net/feeds/question/108838 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/108838/equivalence-between-algebraic-semi-group-structures-and-coalgebra-structures-for Dyke Acland 2012-10-04T18:09:52Z 2012-10-04T18:09:52Z

<p>I was looking at this old question</p> <p><a href="http://mathoverflow.net/questions/44275/hopf-algebra-and-group-structure-correspondence-for-algebraic-varieties" rel="nofollow">http://mathoverflow.net/questions/44275/hopf-algebra-and-group-structure-correspondence-for-algebraic-varieties</a></p> <p>which says that there exists an equivalence between algebraic group structures on an algebraic variety $V$ (over a field) and Hopf algebraic structures on its algebra of regular functions $O(V)$. I would guess that this extends to an equivalence between algebraic semi-groups structures on $V$ and coalgebra structures on $O(V)$. Am I correct here?</p>