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The spin dynamics of cold polarized gases are investigated using the Boltzmann equation. The dispersion relation for spin waves (transverse component of the magnetic moment) and the spin diffusion coefficient of the longitudinal component of the magnetic moment are calculated without using fitting parameters. The spin wave frequency and the diffusion coefficient for rubidium atoms are estimated numerically. [ABSTRACT FROM AUTHOR]

The existence of spin waves of a new type is predicted for ultracold paramagnetic gases with nondegenerate energy levels. The waves are generated by creating a nonequilibrium population in the absence of external polarization and are damped not only by diffusion, but also by a previously ignored mechanism due to level splitting. Theoretical calculations are in fair agreement with experimental observations of spin waves in magnetically trapped clouds of rubidium atoms. [ABSTRACT FROM AUTHOR]

A new type of spin waves that arise in a paramagnetic gas with a nondegenerate energy level system is predicted. Such waves occur without the commonly applied external gas polarization and are only due to the nonequilibrium population of the operating levels. The dispersion law for these waves is derived. [ABSTRACT FROM AUTHOR]

We derive a kinetic equation for a polarized paramagnetic gas that is exact in the Boltzmann (binary) approximation. The equation is written in a compact form and applies to both Fermi and Bose gases in a wide temperature range as long as the Boltzmann approximation remains applicable. The derived equation is used to analyze the conditions for the propagation of spin waves in polarized Fermi and Bose gases. We deduce a universal criterion for the propagation of weakly damped spin waves in a wide temperature range. The criterion is reduced to the condition that the real parts of the particle zero-angle scattering amplitudes (or T matrices) be much larger than their imaginary parts. We derive dispersion equations for spin waves at high and low gas temperatures and show that spin waves can propagate in both these limiting cases. [ABSTRACT FROM AUTHOR]

As a result of an investigation of the real collision integral for paramagnetic atoms, we have obtained a criterion for propagation of spin waves in a spin-polarized Boltzmann gas. The main condition for propagation of weakly damped spin waves is a high anisotropy of the atomic scattering amplitude with predominance of the forward scattering. This condition is different from those suggested in earlier publications. Our results indicate that the range of paramagnetic gases where weakly damped spin waves can propagate at the room temperature is considerably wider than it was assumed previously. One example is vapors of alkali metals (Na, Cs, and Rb), where the degree of electron spin polarization can be very high. [ABSTRACT FROM AUTHOR]

A criterion for the propagation of weakly-damped spin waves is obtained on the basis of a detailed analysis of the quantum collision integral for particles in a paramagnetic polarized Boltzmann gas. It is shown that according to this criterion spin waves can propagate in classical (nonquantum) gases at temperatures close to room temperature. [ABSTRACT FROM AUTHOR]

The dynamics of spin waves in ultracold gases is investigated with allowance for exchange and spin-orbit interaction. The exact basis of atomic states is used taking into account all rotational quantum numbers of the atom. The dispersion relation for spin waves is obtained for fermions and bosons in the hydro-dynamic approximation. [ABSTRACT FROM AUTHOR]

A new type of spin waves that appear in cold paramagnetic gases owing to the spin-orbit interaction has been predicted. The Boltzmann gases of heavy atoms with a nonzero orbital angular momentum are considered. The dispersion relation of the spin waves is determined by the scattering amplitude due to the spin-orbit interaction. [ABSTRACT FROM AUTHOR]