### Stabilization of the Witt Group, by Max Karoubi

Using an idea due to R. Thomason, we define a "homology theory" on the
category of rings which satisfies excision, exactness, homotopy (in
the algebraic sense) and periodicity of order 4. For regular
noetherian rings, we find P. Balmers's higher Witt groups. For more
general rings, this homology is isomorphic to the KT-theory of J.
Hornbostel, inspired by the work of B. Williams. For real or complex
C*-algebras, we recover - up to 2 torsion - topological K-theory.

Max Karoubi <karoubi@math.jussieu.fr>