On the ground state energy of a gas of interacting polarons in a   magnetic field
  The ground-state energy of a three-dimensional polaron gas in a magnetic field is investigated. An upper bound for the ground-state energy is derived within a variational approach which is based on a many-body generalization of the Lee-Low-Pines transformation. The basic contributing ingredients found are the ground-state energy and the static structure factor of the homogeneous electron gas in a magnetic field. Both these quantities are derived in the Hartree-Fock approximation. The resulting ground-state energy of the polaron gas is analyzed as a function of the electron density and of the magnetic field strength. 
K. Putteneers, F. Brosens, S. N. Klimin, J. T. Devreese (TFVS,   Universiteit Antwerpen, Belgium)