Interaction and Quantum Decoherence in Disordered Conductors

We present a nonperturbative approach which allows to evaluate the weak localization correction to the conductivity of disordered conductors in the presence of interactions. The effect of the electron-electron interaction on the magnetoconductance is described by the function A(t)\exp (-f(t)). The dephasing time is determined only by f(t), and this time remains finite down to T=0 due to the electron-electron interactions. In order to establish the relation between our nonperturbative analysis and the perturbative results the effect of interaction on the pre-exponent A(t) should be taken into account. The dephasing time cannot be unambiguously determined from a perturbative calculation.