A Unitary Model Of Black Hole Evaporation

In 1975, Hawking found that black hole can lose its mass through some quantum process, the so called Hawking radiation or black hole evaporation. Unfortunately, the Hawking radiation was found to be completely thermal, violating the quantum unitary condition which postulates that both black hole formation and evaporation should be described well by a underlying quantum gravity theory. This leads to the famous information loss paradox for a black hole.Actually, if general relativity was valid, the spacetime geometry near black hole’s event hori-zon must be smooth in the eyes of an in-falling observer. This means that the vacuum observed by the in-falling observer, the in-falling vacuum, must be entangled between exterior (outgoing) and interior (incoming) modes for the static reference frame. Since the Hawking radiation observed by an outside static observer involves only the exterior modes, the entanglement of the in-falling vacuum is destroyed, leading to a thermal spectrum or information loss. To resolve the information loss paradox, the thermal Hawking radiation must be purified to become a pure state, through en-tangling with some other modes. However, Ahmed Almheiri et al. found that if someone want to purify the Hawking radiation through establishing a new entanglement with some other modes, the monogamy of entanglement would be violated. To obey the monogamy of entanglement, they say that the geometry near black hole’s event horizon would evolve to a high energy firewall, leading to the so called firewall paradox.In this dissertation, we introduce a new model for the black hole evaporation, in which both of the above two paradoxes could be resolved effectively. In fact, this model is based on a modified quantum teleportation, by using of the entangled in-falling vacuum as some medium. First, we introduce a qubit model which serves as a simplified version of our black hole evaporation model.Then, we build our model step by step in the framework of effective field theory. After that,we make a comparison between our model and Hawking’s results, and see how the above two paradoxes can be resolved effectively. Finally, we try to reconstruct black hole thermodynamics based on our model, in particular, we show that the Bekenstein-Hawking entropy may not be a Boltzmann or thermal entropy. In the appendix 1, we give a new interpretation of hκ/c, which may provide some clue to the underlying quantum gravity theory.