7861609
Dimension of the Universe.
The dynamical evolution of the Universe is represented by the wave packet of Hartle and Hawking's ''ground state.'' Its most probable trajectory arises by a quantum tunneling from a gravitational instanton. We discuss the dimensionality of the Universe within the framework of eleven-dimensional supergravity as a true Kaluza-Klein theory. By using some minisuperspace ansatz, it is proved that only S/sub 4/ x S/sub 7/ instantons are possible. From the viewpoint of quantum cosmology, it seems that the main reason the apparent spacetime is four-dimensional is simply that there does not exist any gravitational instanton without a four-dimensional sector in the theory.
118822751
Dimensionality in the Freund–Rubin cosmology
Abstract In the n -dimensional Freund–Rubin model with an antisymmetric tensor field of rank s −1, the dimension of the external spacetime we live in must be min( s , n − s ). This result is a generalization of the previous result in the d =11 supergravity case, where s =4.
118836688
The Cosmological Constant in Quantum Cosmology
Hawking proposed that the cosmological constant is probably zero in quantum cosmology in 1984. By using the right configuration for the wave function of the universe, a complete proof is found very recently.
13157000
REAL TUNNELING AND BLACK HOLE CREATION
We discuss the Hawking theory of quantum cosmology with regard to approximation at the lowest order of the Planck constant. At this level, the quantum scenario will be reduced to its classical evolutions in real and imaginary times. We restrict our attention to the so-called real tunneling case. It can be shown that, even at this level, there still exist some quantum effects, the classical field equation may not hold at the transition surface. One can introduce the concept of constrained gravitational instanton. It may play some important role in the scenario of black hole creation in the inflationary background at the Planckian era of the universe. From the constrained gravitational instanton, the real tunneling can occur through different ways. Consequently, it will lead to the creation of different parts of the black hole spacetime in the de Sitter background. The global aspects of the black hole creation are discussed.
18697416
CAN BLACK HOLES BE CREATED AT THE BIRTH OF THE UNIVERSE
We study the quantum creation of black hole pairs in the (anti-)de Sitter space background. These black hole pairs in the Kerr–Newman family are created from constrained instantons. At the WKB level, for the chargeless and nonrotating case, the relative creation probability is the exponential of (the negative of) the entropy of the universe. Also for the remaining cases of the family, the creation probability is the exponential of (the negative of) one quarter of the sum of the inner and outer black hole horizon areas. In the absence of a general no-boundary proposal for open universes, we treat the creations of the closed and the open universes in the same way.
16241120
The Imaginary Time in the Tunneling Process
By using techniques developed in quantum cosmology, it is found that a tunneling particle spends purely imaginary time on a barrier region. The {\it imaginary} time is associated with the stochastic acausal behaviour of a state, while the {\it real} time is associated with the deterministic causal evolution of a state. For the tunneling case the nonzero imaginary time is associated with the transmission rate of the tunneling process, which is related to the thickness of the barrier. The physical meaning of the zero real time is that the particle instantly jumps from one side of the barrier to the other regardless of the thickness. This leads to the illusion that tunneling particles could actually travel faster than light. The results of recent experiments in quantum optics concerning tunneling time can be thought of as the first experimental confirmation of the existence of imaginary time. Relativity is not violated.
15013
Multisource model for particle production in high-energy hadron-nucleus collisions.