The charge and spin response of a spin--polarized electron gas is
investigated including terms beyond the random phase approximation. We evaluate
the charge response, the longitudinal and transverse spin response, and the
mixed spin--charge response self--consistently in terms of the susceptibility
functions of a non--interacting system. Exchange--correlation effects between
electrons of spin σ and σ′ are included following Kukkonen and
Overhauser, by using spin--polarization dependent generalized Hubbard local
field factors Gσ​± and Gσˉ​±. The general
condition for charge--density and spin--density--wave excitations of the system
is discussed.Comment: 4 pages, latex, no figure