Landau Ghosts and Anti-Ghosts in Condensed Matter and High Density   Hadronic Matter
  It is observed that the ``ghost'' (originally discovered by Landau in quantum electro-dynamics) and its counterparts in other theories are indeed ubiquitous as they occur in a one-loop approximation to any conventional (unbroken) gauge theory. The mechanism is first exposed in its generality via the Dyson equation and a simple but explicit example in condensed matter is provided through the static Clausius-Mossotti and its dynamic counterpart the Lorenz-Lorentz equation. The physical phase transition phenomenon associated with it is found to be super-radiance. We verify quantitatively that water (and many other polar liquids) are indeed super-radiant at room temperature. In quantum chromo-dynamics on the other hand, we encounter, thanks to asymptotic freedom, an ``anti-ghost'' which is closely associated with color confinement. Thus, in QCD, free quarks and glue exist in a super-radiant phase and hadronic matter in the normal one. 
S. Sivasubramanian, Y.N. Srivastava, A. Widom