  Nuclei in dense matter are influenced by the medium. In the cluster mean
field approximation, an effective Schr\"odinger equation for the $A$-particle
cluster is obtained accounting for the effects of the correlated medium such as
self-energy, Pauli blocking and Bose enhancement. Similar to the single-baryon
states (free neutrons and protons), the light elements ($2 \le A \le 4$,
internal quantum state $\nu$) are treated as quasiparticles with energies
$E_{A,\nu}(\vec P; T, n_n,n_p)$. These energies depend on the center of mass
momentum $\vec P$, as well as temperature $T$ and the total densities $n_n,n_p$
of neutrons and protons, respectively. No $\beta$ equilibrium is considered so
that $n_n, n_p$ (or the corresponding chemical potentials $\mu_n, \mu_p$) are
fixed independently.
  For the single nucleon quasiparticle energy shift, different approximate
expressions such as Skyrme or relativistic mean field approaches are well
known. Treating the $A$-particle problem in appropriate approximations, results
for the cluster quasiparticle shifts are given. Properties of dense nuclear
matter at moderate temperatures in the subsaturation density region considered
here are influenced by the composition. This in turn is determined by the
cluster quasiparticle energies, in particular the formation of clusters at low
densities when the temperature decreases, and their dissolution due to Pauli
blocking as the density increases. Our finite-temperature Green function
approach covers different limiting cases: The low-density region where the
model of nuclear statistical equilibrium and virial expansions can be applied,
and the saturation density region where a mean field approach is possible.
