Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Is Bianchi I a Bouncing Cosmology in the Wheeler-DeWitt picture?   We provide a quantum picture for the emergence of a bouncing cosmology,
according to the idea that a semiclassical behavior of the Universe towards the
singularity is not available in many relevant Minisuperspace models. In
particular, we study the Bianchi I model in vacuum adopting the isotropic
Misner variable as an internal clock for the quantum evolution. The isomorphism
between the Wheeler-DeWitt equation in this Minisuperspace representation and
the Klein-Gordon one for a relativistic scalar field allows to identify the
positive and negative frequency solutions as associated to the collapsing and
expanding Universe respectively. We clarify how any Bianchi I localized wave
packet unavoidably spreads when the singularity is approached and therefore the
semiclassical description of the model evolution in the Planckian region loses
its predictability. Then, we calculate the transition amplitude that a
collapsing Universe is turned into an expanding one, according to the standard
techniques of relativistic quantum mechanics, thanks to the introduction of an
ekpyrotic-like matter component which mimics a time-dependent potential term
and breaks the frequency separation. In particular, the transition probability
of this "Quantum Big Bounce" acquires a maximum value when the mean values of
the momenta conjugate to the anisotropies in the collapsing Universe are close
enough to the corresponding mean values in the expanding one, depending on the
variances of the in-going and out-going Universe wave packets. This symmetry
between the pre-Bounce and post-Bounce mean values reflects what happens in the
semiclassical bouncing cosmology, with the difference that here the connection
of the two branches takes place on a pure probabilistic level.

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The categories of this paper are: hep-th
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The categories of this paper are: funct-an
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The categories of this paper are: nucl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: q-bio
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: bayes-an
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The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: nlin
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The categories of this paper are: eess
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The categories of this paper are: solv-int
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The categories of this paper are: math
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The categories of this paper are: chao-dyn