A tensorial description of particle perception in black-hole physics
  In quantum field theory in curved backgrounds, one typically distinguishes between objective, tensorial, quantities such as the Renormalized Stress-Energy Tensor (RSET) and subjective, non-tensorial, quantities such as Bogoliubov coefficients which encode perception effects associated with the specific trajectory of a detector. In this work we propose a way to treat both objective and subjective notions on an equal tensorial footing. For that purpose, we define a new tensor which we will call the Perception Renormalized Stress-Energy Tensor (PeRSET). The PeRSET is defined as the subtraction of the RSET corresponding to two different vacuum states. Based on this tensor we can define perceived energy densities and fluxes. The PeRSET helps to have a more organized and systematic understanding of various results in the literature regarding quantum field theory in black hole spacetimes. We illustrate the physics encoded in this tensor by working out various examples of special relevance. 
Luis C. Barbado, Carlos Barcel\'o, Luis J. Garay and Gil Jannes
gr-qc