The Born - Oppenheimer approach to the matter - gravity system and unitarity

Bertoni, Carlo Maria; Finelli⋆, F.; Venturi, G.

doi:10.1088/0264-9381/13/9/005

Cited by 81 publications

(208 citation statements)

References 16 publications

(33 reference statements)

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“…As a consequence of the presence of such terms no violation of unitarity is found. A similar result has been obtained previously for the purely homogeneous case [24].…”

Section: Discussionsupporting

confidence: 91%

The Born–Oppenheimer method, quantum gravity and matter

Kamenshchik

Tronconi

Venturi

2017

Class. Quantum Grav.

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Abstract. We illustrate and examine diverse approaches to the quantum matter-gravity system which refer to the Born-Oppenheimer (BO) method. In particular we first examine a quantum geometrodynamical approach introduced by other authors in a manner analogous to that previously employed by us, so as to include back reaction and non-adiabatic contributions. On including such effects it is seen that the unitarity violating effects previously found disappear. A quantum loop space formulation (based on a hybrid quantisation, polymer for gravitation and canonical for matter) also refers to the BO method. It does not involve the classical limit for gravitation and has a highly peaked initial scalar field state. We point out that it does not resemble in any way to our traditional BO approach. Instead it does resemble an alternative, canonically quantised, non BO approach which we have also previously discussed.

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“…As a consequence of the presence of such terms no violation of unitarity is found. A similar result has been obtained previously for the purely homogeneous case [24].…”

Section: Discussionsupporting

confidence: 91%

The Born–Oppenheimer method, quantum gravity and matter

Kamenshchik

Tronconi

Venturi

2017

Class. Quantum Grav.

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“…The semiclassical limit for various models has been previously investigated [5,6,7,8,9] by employing a Born-Oppenheimer (BO) decomposition of the corresponding minisuperspace wavefunction [10,11,12]. In particular, in Ref.…”

Section: Introductionmentioning

confidence: 99%

Gravitational collapse of a radiating shell

et al. 2001

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We study the collapse of a self-gravitating and radiating shell of bosonic matter. The matter constituting the shell is quantized and the construction is viewed as a semiclassical model of possible black hole formation. It is shown that the shell internal degrees of freedom are excited by the quantum non-adiabaticity of the collapse and, consequently, on coupling them to a massless scalar field, the collapsing matter emits a burst of coherent (thermal) radiation. The backreaction on the trajectory is also estimated.

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“…It is noticeable that Eqs. (10) do not contain terms corresponding to gravitational fluctuations of the form which is obtained when the momentum Π m enters quadratically [16,17]. This signals the fact that, on restricting the support of the constraints just on the apparent horizon, one is actually freezing most of the quantum fluctuations for the system [18].…”

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confidence: 99%

“…[9], but here we want to employ the more systematic Born-Oppenheimer approach (see, for instance, Ref. [7,16]). First of all, we assume that the complete wavefunction factorizes into "gravitational" (ψ) and "matter" (χ) parts,…”

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confidence: 99%

On time evolution of quantum black holes

Casadio

2001

Physics Letters B

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The time evolution of black holes involves both the canonical equations of quantum gravity and the statistical mechanics of Hawking radiation, neither of which contains a time variable. In order to introduce the time, we apply the semiclassical approximation to the Hamiltonian constraint on the apparent horizon and show that, when the backreaction is included, it suggests the existence of a long-living remnant, similarly to what is obtained in the microcanonical picture for the Hawking radiation.Key words: black holes, Hawking effect, microcanonical ensemble, semiclassical approximation, quantum gravity PACS: 04.70.-s, 04.70.Dy, 04.60.-m A longstanding issue in theoretical physics is how to quantize Einstein gravity. Since in the theory there are constraints whose algebra contains structure functions (which depend on the space-time coordinates), one can conceive (inequivalent [1]) manners of lifting the Hamiltonian and momentum constraints to quantum equations, thus hindering the formal solution to the problem. On a more physical ground, one might notice that it is relevant to have a quantum theory of gravity at our disposal only for systems with very strong (Planck size) gravitational fields, such as those one expects in the early stages of the Universe. Because of Hawking's discovery of black hole evaporation [2], one also expect that quantum (or semiclassical) gravity plays a role in determining the dynamics of the late stages in the life of collapsed objects.In a general situation, one has to deal with the infinite number of degrees of freedom of the gravitational field configurations which are physically distinguished only modulo coordinate transformations. This gives the constraints the form of functional differential equations, for which there is little hope of finding general solutions, and one then tries to reduce the number of degrees 1

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The Born - Oppenheimer approach to the matter - gravity system and unitarity

Cited by 81 publications

References 16 publications

The Born–Oppenheimer method, quantum gravity and matter

The Born–Oppenheimer method, quantum gravity and matter

Gravitational collapse of a radiating shell

On time evolution of quantum black holes

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