Spreading width of giant resonances and the attenuation of zero sound

It is shown that the RPA plus perturbation approach which is commonly used to calculate microscopically the spreading width of Giant Resonances is equivalent to Landau's suggestion that the damping width of zero sound at temperatureT=0 can be obtained by multiplying the classical collision result with an energyω- andT-dependent correction factor [1+(ω/2πkT)²] withT→0.