  We explore how non-equilibrium noise affects spin-torque switching elements
and oscillators. To do so we first discuss the deterministic dynamics of
magnetic tunnel junctions, introducing a convenient set of slow and fast
degrees of freedom. We then derive effective Langevin equation for the slowly
varying energy of precessional orbit and introduce the corresponding energy
noise and energy diffusion coefficient. This allows for the formulation of a
Fokker-Planck equation for the energy density distribution. We use it to
analyse switching time distribution as well as the shape of the optimal
spin-current pulse, which minimizes Joule losses of a switch. Finally we derive
a generic expression for the linewidth of a spin-torque oscillator and discuss
its dependence on temperature, spin-current amplitude and other parameters.
