文摘
Quillen introduced a new -theory of nonunital rings in Quillen (1996) [1] and showed that, under some assumptions (weaker than the existence of unity), this new theory agrees with the usual algebraic -theory. For a field k of characteristic 0, we introduce higher nonunital K-theory of k-algebras, denoted as KQ, which extends Quillen’s original definition of the functor. We show that the KQ-theory is Morita invariant and satisfies excision connectively, in a suitable sense, on the category of idempotent k-algebras. Using these two properties we show that the KQ-theory agrees with the topological K-theory of stable C*-algebras. The machinery enables us to produce a DG categorical formalism of topological homological -duality using bivariant K-theory classes. A connection with strong deformations of C*-algebras and some other potential applications to topological field theories are discussed towards the end.