Quantum decoherence and weak localization at low temperatures

With the aid of the Keldysh technique we develop a path-integral formalism which allows us to nonperturbatively study the quantum dynamics of electron s in a disordered metal in the presence of interactions. We derive a formal ly exact equation of motion for the electron density matrix and demonstrate that the effect of interaction of the electron with other electrons in a d isordered metal is equivalent to that of an effective dissipative environme nt, We obtain nonperturbative results for the weak localization correction to the conductance delta sigma and show that the effective decoherence leng th extracted from Sa remains finite down to T=0 due to electron-electron in teractions. [S0163-1829(98)06942-2].