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  • Hawking
  • Physical review. D, Particles and fields
  • 1991
It has been suggested that an advanced civilization might have the technology to warp spacetime so that closed timelike curves would appear, allowing travel into the past. This paper examines this(More)
An interesting two-dimensional model theory has been proposed that allows one to consider black-hole evaporation in the semiclassical approximation. The semiclassical equations will give a(More)
We consider two quantum cosmological models with a massive scalar field: an ordinary Friedmann universe and a universe containing primordial black holes. For both models we discuss the complex(More)
  • Hawking
  • Physical review. D, Particles and fields
  • 1988
Any reasonable theory of quantum gravity will allow closed universes to branch off from our nearly flat region of spacetime. I describe the possible quantum states of these closed universes. They(More)
It is argued that the observed thermodynamic arrow of time must arise from the boundary conditions of the Universe. We analyze the consequences of the no-boundary proposal, the only reasonably(More)
  • Hawking
  • Physical review. D, Particles and fields
  • 1996
One would expect spacetime to have a foam-like structure on the Planck scale with a very high topology. If spacetime is simply connected (which is assumed in this paper), the non-trivial homology(More)