Let G be a finite group, X be a compact G-space. In this note we study the (Z + × Z/2Z)-graded algebradefined in terms of equivariant K-theory with respect to wreath products as a symmetric algebra. More specifically, let H be another finite group and Y be a compact H-space, we give a decomposition of F q G×H (X × Y ) in terms of F q G (X) and F q H (Y ). For this, we need to study the representation theory of pullbacks of groups. We discuss also some applications of the above result to equivariant connective K-homology.
NotationIn this note we denote by S n the symmetric group in n letters. Let G be a finite group, let g, g ′ ∈ G, we say that g and g ′ are conjugated in G (denoted by g ∼ G g ′ ) if there is s ∈ G such that g = sg ′ s −1 . We denote byto the conjugacy class of g in G (or simply by [g] when G is clear from the context). We denote by G * the set of conjugacy classes of G. We denote by C G (g) the centralizer of g in G. Also R(G) will be the complex representation ring of G, with operations given by direct sum and tensor product, and generated as abelian group by the isomorphism classes of irreducible representations of G. The class function ring of G is the set Class(G) = {f : G → C | f is constant in conjugacy classes} with the usual operations.