Singularity avoidance for collapsing quantum dust in the Lemaître-Tolman-Bondi model

Kiefer, Claus; Schmitz, Tim

doi:10.1103/physrevd.99.126010

Cited by 40 publications

(62 citation statements)

References 59 publications

(141 reference statements)

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“…This statement overemphasizes the role of quantum geometry, while it ignores the fact that fluctuation effects explain much of the volume and density bounds obtained in loop quantum cosmology. Potential singularity resolution in loop quantum cosmology is therefore not dissimilar from what has been found in certain Wheeler-DeWitt-type quantizations; see for instance [81,82,83,84]. The mistake is repeated in "In LQC the repulsive force has its origin in quantum geometry rather than quantum matter and it always overwhelms the classical gravitational attraction."…”

Section: What's Left?mentioning

confidence: 96%

Critical Evaluation of Common Claims in Loop Quantum Cosmology

Bojowald

2020

Universe

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A large number of models have been analyzed in loop quantum cosmology, using mainly minisuperspace constructions and perturbations. At the same time, general physics principles from effective field theory and covariance have often been ignored. A consistent introduction of these ingredients requires substantial modifications of existing scenarios. As a consequence, none of the broader claims made mainly by the Ashtekar school -such as the genericness of bounces with astonishingly semiclassical dynamics, robustness with respect to quantization ambiguities, the realization of covariance, and the relevance of certain technical results for potential observations -hold up to scrutiny. Several useful lessons for a sustainable version of quantum cosmology can be drawn from this outcome. * e-mail address: bojowald@gravity.psu.edu 1 All quotations from [1] given in this paper refer to the second preprint version.

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Section: What's Left?mentioning

confidence: 96%

Critical Evaluation of Common Claims in Loop Quantum Cosmology

Bojowald

2020

Universe

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“…The last equation is effectively a Schrödinger equation with dust proper time as the time parameter. This Schrödinger equation we have discussed in [6] for Lemaître-Tolman-Bondi collapse. We will briefly recapitulate the results of this previous work and how they relate to the OS model.…”

Section: A the Comoving Observermentioning

confidence: 99%

“…We have discussed in a previous work a quantization of the Lemaître-Tolman-Bondi (LTB) model for inhomogeneous, spherically symmetric dust collapse, implementing unitary evolution from the point of view of the comoving observer [6]. There we have shown that the classical singularity is avoided by a bounce: instead of fully collapsing to a singularity the matter configuration re-expands.…”

Section: Introductionmentioning

confidence: 99%

“…Concerning the former, proposals include the vanishing of the apparent horizon during the bounce [12][13][14][15] and a transition between black-and white hole horizon via a superposition of the two [9,16]. We have seen in [6] that the latter is a plausible scenario for the LTB model. The mechanism by which quantum gravitational effects reach the horizon, usually a low curvature region of spacetime, is also a matter of debate.…”

Section: Introductionmentioning

confidence: 99%

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Towards a quantum Oppenheimer-Snyder model

Schmitz

2020

Phys. Rev. D

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We present a consistent canonical formulation of the flat Oppenheimer-Snyder model, including the Schwarzschild exterior. The switching between comoving and stationary observer is realized by promoting the coordinate transformation between dust proper time and Schwarzschild-Killing time to a canonical one. This leads to two different forms of the Hamiltonian constraint, both (almost) deparameterizable with regard to one of these times. A preliminary quantization of these constraints reveals a consistent picture for both observers: the singularity is avoided by a bounce.

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“…In 2009, F. Amemiya and T. Koike based on the equation (2) (in the proper time coordinate) have shown that the initial singularity of the flat FRW universe can be avoided by the quantum effect [8]. There are also other works (see [9,10] and the related references there in) showing that the singularity can be avoided in the canonical quantum cosmology. In 2015, H. Maeda using the equation ( 2) studied the evolution of the quantum universe driven by the cosmological constant (dark energy) [11].…”

Section: Introductionmentioning

confidence: 99%

Quantum cosmology of the flat universe via closed real-time path integral

Wang¹,

Wang²

2021

Preprint

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Understanding the evolution of the universe through the quantum cosmology approach is still not fully realized yet. Introducing the Brown-Kuchař dust field as the time variable, we studied the evolution of the quantum universe nonperturbatively by the closed real time path integral. We evaluated the influence functional of the massless scalar field coupled with the flat FRW universe. By setting the initial state of the spacetime as a Gaussian wave packet, we studied the evolution of the quantum universe. In the proper time coordinate, if the evolution of the universe is driven by the thermal radiation or the non-relativistic particles, we show a quantum spacetime can decohere to a classical spacetime. As the temperature of the thermal radiation decreases, the small quantum universe grows up to a larger classical universe. We show that whatever the form of the matter is, the classical trajectory of the universe is always consistent with the quantum evolution of the wave packet. We find that in different scenarios, the variation of the coherence is always consistent with the variation of the Gibbs entropy. We also studied the transition of the flat FRW universe starting from certain initial state of the spacetime. We illustrate that the transition probability is closely related to the Vilenkin's tunneling from nothing scenario. We show that the quantum universe can grow only when the initial state of the spacetime is distributed. We also show that under the larger cosmological constant or the higher radiation temperature a small universe has a higher chance of the transition to a bigger universe. Finally, we point out that in the proper time coordinate, the minimal coupling of the free massless field with the flat FRW spacetime can generally give rise to the memory characterized by non-Markovian correlations.

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Singularity avoidance for collapsing quantum dust in the Lemaître-Tolman-Bondi model

Cited by 40 publications

References 59 publications

Critical Evaluation of Common Claims in Loop Quantum Cosmology

Critical Evaluation of Common Claims in Loop Quantum Cosmology

Towards a quantum Oppenheimer-Snyder model

Quantum cosmology of the flat universe via closed real-time path integral

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