  The quintessential description of Kondo physics in equilibrium is obtained
within a scaling picture that shows the buildup of Kondo screening at low
temperature. For the non-equilibrium Kondo model with a voltage bias the key
new feature are decoherence effects due to the current across the impurity. In
the present paper we show how one can develop a consistent framework for
studying the non-equilibrium Kondo model within a scaling picture of
infinitesimal unitary transformations (flow equations). Decoherence effects
appear naturally in third order of the beta-function and dominate the
Hamiltonian flow for sufficiently large voltage bias. We work out the spin
dynamics in non-equilibrium and compare it with finite temperature equilibrium
results. In particular, we report on the behavior of the static spin
susceptibility including leading logarithmic corrections and compare it with
the celebrated equilibrium result as a function of temperature.
