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On signature transition and compactification in Kaluza-Klein cosmology

F Darabi and H R Sepangi

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We consider an empty (4 + 1)-dimensional Kaluza-Klein universe with a negative cosmological constant and a Robertson-Walker-type metric. It is shown that the solutions to the Einstein field equations have a degenerate metric and exhibit transitions from a Euclidean to a Lorentzian domain. We then suggest a mechanism, based on signature transition which leads to compactification of the internal space in the Lorentzian region as a ~ |Lambda|1/2. With the assumption of a very small value for the cosmological constant we find that the size of the universe R and the internal scale factor a would be related according to Ra ~ 1 in the Lorentzian region. The corresponding Wheeler-DeWitt equation has an exact solution in the mini-superspace giving rise to a quantum state which peaks in the vicinity of the classical solutions undergoing signature transition.


PACS

98.80.Qc Quantum cosmology

98.80.Es Observational cosmology (including Hubble constant, distance scale, cosmological constant, early Universe, etc)

04.50.-h Higher-dimensional gravity and other theories of gravity

04.60.Kz Lower dimensional models; minisuperspace models

04.20.-q Classical general relativity

MSC

83C05 Einstein's equations (general structure, canonical formalism, Cauchy problems)

83F05 Cosmology

83E15 Kaluza-Klein and other higher-dimensional theories

83C15 Exact solutions

Subjects

Gravitation and cosmology

Astrophysics and astroparticles

Dates

Issue 5 (May 1999)

Received 13 August 1998, in final form 21 December 1998



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