Quantum cosmology and the arrow of time

Kiefer, Claus

doi:10.1590/s0103-97332005000200014

Cited by 10 publications

(13 citation statements)

References 12 publications

(23 reference statements)

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“…The entropy reaches the minimum value at the bounce while saturated for s → ±∞. This behavior is qualitatively similar to what was predicted by the von Neumann entropy with environmental degrees of freedom taken into account [22,23].…”

Section: Entropysupporting

confidence: 84%

“…The irrelevant degrees of freedom may play a role of the environment that causes decoherence of the sector parametrized by the relevant degrees of freedom as the scale factor. Making some qualitative analysis of the Wheeler-DeWitt equation one may show that the resulting von Neumann entropy is a monotonically increasing function of a scale factor for the FRW model [22,23]. This is in agreement with expectations based on thermodynamical arguments for the expanding Universe.…”

Section: Entropysupporting

confidence: 82%

“…Moreover, such dependence indicates that quantum entropy should decrease in the contracting Universe. This may suggest, by applying the second law of thermodynamics, that the arrow of time is directed out of the bounce and only expansion has physical meaning [23].…”

Section: Entropymentioning

confidence: 99%

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Gaussian state for the bouncing quantum cosmology

Mielczarek

Piechocki

2012

Phys. Rev. D

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We present results concerning propagation of the Gaussian state across the cosmological quantum bounce. The reduced phase space quantization of loop quantum cosmology is applied to the Friedman-Robertson-Walker universe with a free massless scalar field. Evolution of quantum moments of the canonical variables is investigated. The covariance turns out to be a monotonic function so it may be used as an evolution parameter having quantum origin. We show that for the Gaussian state the Universe is least quantum at the bounce. We propose explanation of this counter-intuitive feature using the entropy of squeezing. The obtained time dependence of entropy is in agreement with qualitative predictions based on von Neumann entropy for mixed states. We show that, for the considered Gaussian state, semiclassicality is preserved across the bounce, so there is no cosmic forgetfulness.Comment: 7 pages, 7 figures; matches version published in Phys. Rev.

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Section: Entropysupporting

confidence: 84%

Section: Entropysupporting

confidence: 82%

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Gaussian state for the bouncing quantum cosmology

Mielczarek

Piechocki

2012

Phys. Rev. D

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“…Then, k m can be considered the natural cut-off of the model. Let us also note that a similar behavior of the modes of the universe would be obtained for a non-massless scalar field provided that the potential of the scalar field, V(ϕ), satisfies the boundary condition [38,39], V(ϕ) → 0 for a → 0.…”

Section: Open Questions In Cosmology 206supporting

confidence: 57%

“…The consideration of the scale factor as a time variable within a single universe is a tricky task (see Refs. [23,30,34,[38][39][40]78]) that will partially be addressed on subsequent sections.…”

Section: Third Quantization Formalismmentioning

confidence: 99%

Inter-Universal Entanglement

Robles-Pérez¹

2012

Open Questions in Cosmology

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Initial conditions for bubble universes

McInnes

2008

Phys. Rev. D

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The "bubble universes" of Coleman and De Luccia play a crucial role in string cosmology. Since our own Universe is supposed to be of this kind, bubble cosmology should supply definite answers to the long-standing questions regarding cosmological initial conditions. In particular, it must explain how an initial singularity is avoided, and also how the initial conditions for Inflation were established. We argue that the simplest non-anthropic approach to these problems involves a requirement that the spatial sections defined by distinguished bubble observers should not be allowed to have arbitrarily small volumes. Casimir energy is a popular candidate for a quantum effect which can ensure this, but [because it violates energy conditions] there is a danger that it could lead to non-perturbative instabilities in string theory. We make a simple proposal for the initial conditions of a bubble universe, and show that our proposal ensures that the system is non-perturbatively stable. Thus, low-entropy conditions can be established at the beginning of a bubble universe without violating the Second Law of thermodynamics and without leading to instability in string theory. These conditions are inherited from the ambient spacetime.

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Quantum cosmology and the arrow of time

Cited by 10 publications

References 12 publications

Gaussian state for the bouncing quantum cosmology

Gaussian state for the bouncing quantum cosmology

Inter-Universal Entanglement

Initial conditions for bubble universes

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