Spectral probes of the holographic Fermi groundstate: dialing between   the electron star and AdS Dirac hair
  We argue that the electron star and the AdS Dirac hair solution are two limits of the free charged Fermi gas in AdS. Spectral functions of holographic duals to probe fermions in the background of electron stars have a free parameter that quantifies the number of constituent fermions that make up the charge and energy density characterizing the electron star solution. The strict electron star limit takes this number to be infinite. The Dirac hair solution is the limit where this number is unity. This is evident in the behavior of the distribution of holographically dual Fermi surfaces. As we decrease the number of constituents in a fixed electron star background the number of Fermi surfaces also decreases. An improved holographic Fermi groundstate should be a configuration that shares the qualitative properties of both limits. 
Mihailo Cubrovic, Yan Liu, Koenraad Schalm, Ya-Wen Sun, and Jan Zaanen
hep-th cond-mat.str-el cond-mat.supr-con