Exact Solutions for Boson-Fermion Stars in (2+1) dimensions
  We solve Einstein equations coupled to a complex scalar field with infinitely large self-interaction, degenerate fermions, and a negative cosmological constant in $(2+1)$ dimensions. Exact solutions for static boson-fermion stars are found when circular symmetry is assumed. We find that the minimum binding energy of boson-fermion star takes a negative value if the value of the cosmological constant is sufficiently small. 
Kenji Sakamoto and Kiyoshi Shiraishi (Yamaguchi University)