A $C^*$-algebraic Schoenberg theorem
A $C^*$-algebraic Schoenberg theorem
Let ๐ be a C * -algebra, G a compact abelian group, ฯ an action of G by *-automorphisms of ๐,๐ ฯ the fixed point algebra of ฯ and ๐ F the dense sub-algebra of G-finite elements in ๐. Further let H be a linear operator from ๐ F into โฆ