  The high density effective theory recently introduced by Hong and Hsu to
describe ultradense relativistic fermionic matter is used to calculate the
tree-level forward scattering amplitude between two particles at the Fermi
surface. While the direct term correctly reproduces that of the underlying
gauge theory, the exchange term has the wrong sign. The physical consequences
are discussed in the context of Landau's theoretical description of the Fermi
liquid.
