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Recent models in quantum cosmology make use of the concept of imaginary time. These models all conjecture a join between regions of imaginary time and regions of real time. We examine the model of James Hartle and Stephen Hawking to argue that the various ‘no-boundary’ attempts to interpret the transition from imaginary to real time in a logically consistent and physically significant way all fail. We believe this conclusion also applies to ‘quantum tunneling’ models, such as that proposed by Alexander Vilenkin. We conclude, therefore, that the notion of ‘emerging from imaginary time’ is incoherent. A consequence of this conclusion seems to be that the whole class of cosmological models appealing to imaginary time is thereby refuted.

DOI: 10.1007/BF00413497

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