Abstract: |
We generalize the vacuum-Unruh effect to arbitrary excited states in the Fock space, and find that the Unruh mode at the horizon induces coherent excitation on the canonical background ensemble measured by an accelerated observer. When there is only one type of Unruh mode in the system, for example the ones outgoing from a black hole horizon, the mapping from an arbitrary density matrix on the maximal foliation to a vector space spanned by the pseudo-thermal density matrix on the partitioned spacetime wedge is one-to-one. We thus propose that the information of the particles that fell into the black hole horizon is at least partially retrievable by measuring the deviation of the Hawking radiation from the black body radiation spectrum. This work shows that the long-standing black hole information confusion might come from overlooking the possibility that the information could be preserved much better than we have expected in a seemingly non-unitary process, when the partitions of the system are strongly entangled. |