When the wave amplitudes are small, the nonlinearity is weak and the wave periods, determined by the linear dynamics, are much smaller than the characteristic time at which different wave modes exchange energy. In the other words, weak nonlinearity results in a timescale separation and this fact is exploited in WT to describe the slowly changing wave statistics by averaging over the fast linear oscillations.

- Evolution equations for the PDF's, moments and spectrum.
- Preservation of the RPA property.
- Steady state solutions.

Dr Yuri V Lvov 2007-01-16