Hawking Radiation, Gravitational Anomaly and Conformal Symmetry - the   Origin of Universality -
  The universal behavior of Hawking radiation is originated in the conformal symmetries of matter fields near the black hole horizon. We explain the origin of this universality based on (1) the gravitational anomaly and its higher-spin generalizations and (2) conformal transformation properties of fluxes. 
Satoshi Iso