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Deformation Theory Seminar

Monday, November 1, 2021 - 2:00pm

Naruki Masuda

Johns Hopkins


University of Pennsylvania

zoom. 91549738223

The associahedra is a sequence of polytopes that controls higher associative algebraic structures. Its concreteness allows explicit combinatorial manipulation, e.g. a (chain complex level) definition of A_\infty algebras. 
I will explain “the magical formula” for the diagonal map of the associahedra that gives a computable description of the tensor product of two A_\infty algebras.
It is derived from a general construction, motivated by the theory of fiber polytopes, of a "polytopal" approximation for the diagonal of any polytope. For simplices, it recovers the classical Alexander-Whitney maps.

Bonus: compatibility with the diagonal construction forces a unique polytopal operad structure on associahedra, which (surprisingly) has never been given explicitly. This is joint work with Thomas, Tonks, and Vallette.