Last gasp of a black hole: unitary evaporation implies non-monotonic   mass loss
  We show within the usual two-dimensional approximation that unitarity and the restoration of Minkowski vacuum correlations at the end of black hole evaporation impose unexpected constraints on its mass loss rate: before disappearing the black hole emits one or more negative energy burst, leading to a temporary increase of its mass. 
Eugenio Bianchi, Matteo Smerlak
gr-qc hep-th