Orateur
Erik Christensen
(Univ. Copenhagen)
Description
Commutators in NCG like $[D,a]$ take the form of a Schur multiplication $\big( (\lambda_i - \lambda_j)a_{ij})\big). $ Schur multiplication of matrices is also named Hadamard multiplication. It is shown that inside many C$^*$-algebras, which have the form of a crossed product of a C$^*$-algebra by a discrete group, the obvious Hadamard product, given as $(\sum_g U_g a_g) \star_H (\sum_g U_gb_g ):= \sum_g U_ga_gb_g,$ has many nice properties such as having a Stinespring representation, and the Schur product is a special case of this.
Auteur principal
Erik Christensen
(Univ. Copenhagen)
