  The low temperature properties of a wide range of many-fermion systems are
well understood within the framework of Landau's theory of Fermi liquids. The
low-energy physics of these systems is governed by interacting fermionic
quasiparticles with momenta and energies near a Fermi surface in momentum
space. Nonequilibrium properties are described by a kinetic equation for the
distribution function for quasiparticles proposed by Landau. Quasiparticle
interactions with other quasiparticles, phonons or impurities lead to internal
forces acting on a distribution of nonequilibrium quasiparticles, as well as
collision processes that ultimately limit the transport of mass, heat, charge
and magnetization, as well as limit the coherence times of quasiparticles. For
Fermi liquids that are close to a second order phase transition, e.g. Fermi
liquids that undergo a superfluid transition, \emph{incipient} Cooper pairs -
long-lived fluctuations of the ordered phase - provide a new channel for
scattering quasiparticles, as well as corrections to internal forces acting on
the distribution of nonequilibrium quasiparticles. We develop the theory of
quasiparticle transport for Fermi liquids in the vicinity of a BCS-type
superfluid transition starting from Keldysh's field theory for non-equilibrium,
strongly interacting fermions. The leading corrections to Fermi liquid theory
for non-equilibrium quasiparticle transport near a Cooper instability arise
from the virtual emission and absorption of incipient Cooper pairs. Our theory
is applicable to quasiparticle transport in superconductors, nuclear matter and
the low temperature phases of liquid $^3$He. As an implementation of the theory
we calculate the pairing fluctuation corrections to the attenuation of zero
sound in liquid $^3$He near the superfluid transition and demonstrate
quantitative agreement with experimental results.
