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We consider a normal metal - superconductor (N-S) junction in the regime,when electrons in the normal metal are driven out of equilibrium. We show thatthe non-equilibrium fluctuations of the electron density in the N-layer causethe fluctuations of the phase of the order parameter in the S-layer. As aresult, the density of states in the superconductor deviates from the BCS form,most notably the density of states in the gap becomes finite. This effect canbe viewed as a result of the time reversal symmetry breaking due to thenon-equilibrium, and can be described in terms of a low energy collective modeof the junction, which couples normal currents in N-layer and supercurrents.This mode is analogous to the Schmid-Sch\"{o}n mode. To interpret theirmeasurements of the tunneling current, Pothier {\em et. al} [Phys. Rev. Lett.{\bf 79}, 3490 (1997)] had to assume that the energy relaxation rate in thenormal metal is surprisingly high. The broadening of the BCS singularity of thedensity of states in the S-layer manifest itself similarly to the broadening ofthe distribution function. Mechanism suggested here can be a possibleexplanation of this experimental puzzle. We also propose an independentexperiment to test our explanation.Comment: 16 pages, 2 .eps figure

Theory of interaction effects in normal-metal–superconductor junctions out of equilibrium