terms) as imaginary (pole) and real (principal) parts of the quasiparticle interaction function. These molecular field terms with complicated analytical structure do not vanish completely, as was assumed earlier, in the Boltzmann region, but contribute to higher-order density terms. With an emphasis on quantum gases, we discuss how to reconcile various physical assumptions inherent to different kinetic approaches to dilute gases.

DOI: 10.1103/physrevb.52.6808

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Theory of transverse spin dynamics in a polarized Fermi liquid and an itinerant ferromagnet

V. P. Mineev

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Esteban Calzetta, B. L. Hu

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Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fieldsMay 15, 1988539 citations

{\mathit{I}}_{2}

{k}^{2}

with a complex diffusion coefficient such that the damping has a finite value proportional to the quasiparticles scattering rate at

T=0

. This behavior of a polarized Fermi liquid contrasts with the behavior of a Heisenberg ferromagnet in the hydrodynamic regime where the transverse spin-wave attenuation appears in terms proportional to

{k}^{4}

. The reactive part of the diffusion coefficient in a paramagnetic state at

T=0

proves to be inversely proportional to the magnetization whereas in a ferromagnetic it is directly proportional to the magnetization. The dissipative part of the diffusion coefficient at

T=0

in the paramagnetic state is polarization independent, whereas in the ferromagnetic state it is proportional to the square of the magnetization. Moreover, the spin wave spectrum in a ferromagnetic Fermi liquid proves to be unstable demonstrating the difficulty of applying a Fermi liquid description to itinerant ferromagnetism.