De la K-théorie algébrique vers la K-théorie hermitienne

In this Note, we introduce a new morphism between algebraic and hermitian K-theory. The topological analog is the Adams operation ψ2 in real K-theory. From this morphism, we deduce a lower bound for the higher algebraic K-theory of a ring A in terms of the classical Witt group of the ring A⊗Aop. To cite this article: M. Karoubi, C. R. Acad. Sci. Paris, Ser. I 341 (2005).