18,628 research outputs found
A canonical transformation and the tunneling probability for the birth of an asymptotically DeSitter universe with dust
In the present work, we study the quantum cosmology description of closed
Friedmann-Robertson-Walker models in the presence of a positive cosmological
constant and a generic perfect fluid. We work in the Schutz's variational
formalism. If one uses the scale factor and its canonically conjugated momentum
as the phase space variables that describe the geometrical sector of these
models, one obtains Wheeler-DeWitt equations with operator ordering
ambiguities. In order to avoid those ambiguities and simplify the quantum
treatment of the models, we introduce new phase space variables. We explicitly
demonstrate that the transformation leading from the old set of variables to
the new one is canonical. In order to show that the above canonical
transformations simplify the quantum treatment of those models, we consider a
particular model where the perfect fluid is dust. We solve the Wheeler-DeWitt
equation numerically using the Crank-Nicholson scheme and determine the time
evolution of the initial wave function. Finally, we compare the results for the
present model with the ones for another model where the only difference is the
presence of a radiative perfect fluid, instead of dust.Comment: Revtex4, 18 pages, 2 EPS figure
Reply to "Comment on 'Quantization of FRW spacetimes in the presence of a cosmological constant and radiation'"
The Comment by Amore {\it et al.} [gr-qc/0611029] contains a valid criticism
of the numerical precision of the results reported in a recent paper of ours
[Phys. Rev. D {\bf 73}, 044022 (2006)], as well as fresh ideas on how to
characterize a quantum cosmological singularity. However, we argue that,
contrary to what is suggested in the Comment, the quantum cosmological models
we studied show hardly any sign of singular behavior.Comment: 4 pages, accepted by Physical Review
Avaliação das características físicas das sementes de cultivares de soja especiais para alimentação humana no processamento de extrato solúvel de soja.
Aspectos biológicos de Planococcus sp. (Hemiptera: Pseudococcidae) em videira (Vitis vinifera L.).
Determinação de isoflavonas e inibidor de tripsina de kunitz em grãos e extratos solúveis de soja, obtidos de cultivares especiais para alimentação humana.
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