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Paper: hep-th/9305165
From: Justin D Hayward <J.D.Hayward@damtp.cambridge.ac.uk>
Date: Fri, 28 May 93 17:05 BST
Date (revised): Mon, 31 May 93 12:41:39 BST

Quantum Coherence in Two Dimensions, S.W.Hawking & J.D.Hayward, 11 pages,
DAMTP-R93/15, CALT-68-1861, Tex, 3 appended uuencoded figures.
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Abstract:The formation and evaporation of two dimensional black holes
 are discussed.
It is shown that if the radiation in minimal scalars has positive energy,
there must be a global event horizon or a naked singularity. The former would
imply loss of quantum coherence while the latter would lead to an even worse
breakdown of predictability. CPT invariance would suggest that there ought
to be past horizons as well. A way in which this could happen with wormholes
is described.
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