The recently developed theory of partial actions of discrete groups on C-algebras is extended. A related concept of actions of inverse semigroups on C-algebras is defined, including covariant representations and crossed products. The main result is that every partial crossed product is a crossed product by a semigroup action.

Let G be a locally compact group. We show that the category A(G) of actions of G on C∗-algebras (with equivariant nondegenerate ∗-homomorphisms into multiplier algebras) is equivalent, via a full-crossed-product functor, to a comma category of maximal coactions of G under the comultiplication (C∗(G), δG); and also that A(G) is equivalent, via a reduced-crossed-product functor, to a comma catego...

tive radius r. Let the center Xo be the sequence {&?}, and let 5 be chosen so large that 2~~ + 2~ s 2 + • • • k Q s. If we define xi as (ki, &2> ' * • » $j j8+i, is+2, • • • ), then xi belongs to K and limn fn(xi) = + °°Consequently xi cannot be a point of Up and this contradiction establishes U as a set of the f...

The aim is the theorems of the title and the corollary that the tensor product of two free crossed resolutions of groups or groupoids is also a free crossed resolution of the product group or groupoid. The route to this corollary is through the equivalence of the category of crossed complexes with that of cubical ω-groupoids with connections where the initial definition of the tensor product li...