  Extracting macroscopic properties of a system from microscopic interactions
has always been an interesting topic with the most diverse applications. Here,
we use the quantum Boltzmann equation to investigate the density matrix
evolution of a system of nucleons. Using the quantum field theory tools for
constructing the density matrix operators and calculating the interactions is
the main advantage of this equation. The right-hand side of this equation
involves forward scattering and usual collision terms. As examples of
application, we calculate the standard Bloch equations for the nucleon system
in the presence of a constant and an oscillating magnetic field from the
forward scattering term. We find the longitudinal and transverse (decoherence)
relaxation times from the collision term by considering the nucleon-nucleon
scattering.
