Black Hole Field Theory with a Firewall in two spacetime dimensions
  We propose that the vacuum state of a scalar field around a black hole is a modified Unruh vacuum. In (1+1) dimensions, we show that a free-faller close to such an horizon can be modelled as an inertial observer in a modified Minkowski vacuum. The modification allows for information-leaking correlations at high frequencies. Using a Gaussian detector centred at $k_0$, we find that the expectation value of the number operator for a detector crossing the horizon is proportional to $1/|k_0|$, implying that the free-faller will observe unbounded numbers of high energy photons, i.e. a firewall. 
C. T. Marco Ho, Daiqin Su, Robert B. Mann and Timothy C. Ralph
gr-qc hep-th quant-ph