Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unitarity From a Smooth Horizon?   Under semiclassical evolution, black holes retain a smooth horizon but fail
to return information. Yet, the Ryu-Takayanagi prescription computes the
boundary entropy expected from unitary CFT evolution. We demonstrate this in a
novel setting with an asymptotic bulk detector, eliminating an assumption about
the entanglement wedge of auxiliary systems.
  We consider three interpretations of this result. (i) At face value,
information is lost in the bulk but not in the CFT. This conflicts with the
AdS/CFT dictionary. (ii) No unique QFT state (pure or mixed) governs all
detector responses to the bulk Hawking radiation. This conflicts with the
existence of an S-matrix. (iii) Nonlocal couplings to the black hole interior
cause asymptotic detectors to respond as though the radiation was pure, even
though it is naively thermal. This invalidates the standard interpretation of
the semiclassical state, including its smoothness at the horizon.
  We conclude that unitary boundary evolution requires asymptotic bulk
detectors to become unambiguously pure at late times. We ask whether the RT
prescription can still reproduce the boundary entropy in this bulk scenario. We
find that this requires a substantial failure of semiclassical gravity in a
low-curvature region, such as a firewall that purifies the Hawking radiation.
  Finally, we allow that the dual to semiclassical gravity may be an ensemble
of unitary theories. This appears to relax the tensions we found: the ensemble
average of out-states would be mixed, but the ensemble average of final
entropies would vanish.

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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: funct-an
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The categories of this paper are: stat
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The categories of this paper are: cond-mat
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The categories of this paper are: econ
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The categories of this paper are: supr-con
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The categories of this paper are: math
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The categories of this paper are: physics
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The categories of this paper are: math-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
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The categories of this paper are: nlin
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The categories of this paper are: patt-sol
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The categories of this paper are: eess