Signatures of quantum gravity in a Born–Oppenheimer context

Kamenshchik, Alexander Yu.; Tronconi, Alessandro; Venturi, G.

doi:10.1016/j.physletb.2014.05.028

Cited by 41 publications

(53 citation statements)

References 27 publications

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“…We have also analysed the connection between the relational view adopted in this paper with another popular approach to the "problem of time": the semiclassical emergence of "WKB time" [24,25,39,39,40,40,49]. This approach is relevant because many important phenomenological applications of quantum cosmology have been developed in this "semiclassical" framework [41][42][43][44][45][46][47][48]. Thus, it is worthwhile to understand its relation to the more complete quantum theory based on the physical Hilbert space and associated quantum Dirac observables.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, the explicit connection between this relational view and other approaches to the "problem of time" has remained unclear. In particular, a popular "solution" is the "semiclassical emergence of time": time only exists when the wave function(al) of the gravitational field is in a semiclassical regime (see [24,25,39,40] for a review and [41][42][43][44][45][46][47][48] for phenomenological applications). For this reason, this emergent semiclassical time is often referred to as "WKB time" [39,40,49].…”

Section: Introductionmentioning

confidence: 99%

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Construction of quantum Dirac observables and the emergence of WKB time

Chataignier

2020

Phys. Rev. D

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We describe a method of construction of gauge-invariant operators (Dirac observables or "evolving constants of motion") from the knowledge of the eigenstates of the gauge generator of time-reparametrisation invariant mechanical systems. These invariant operators evolve unitarily with respect to an arbitrarily chosen time variable. We emphasise that the dynamics is relational, both in the classical and quantum theories. In this framework, we show how the "emergent WKB time" often employed in quantum cosmology arises from a weak-coupling expansion of invariant transition amplitudes, and we illustrate an example of singularity avoidance in a vacuum Bianchi I (Kasner) model. * Gauge conditions of the form given in (5) are sufficient for our purposes, although more general gauge conditions are possible [12].† This corresponds to the statement that invariant extensions are obtained by writing gauge-fixed quantities in an arbitrary gauge.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Construction of quantum Dirac observables and the emergence of WKB time

Chataignier

2020

Phys. Rev. D

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“…Finally the analysis performed was based on Planck datasets released in 2015 , include the Planck TT data with polarization at low l (PL) and the data of the BICEP2/Keck Array-Planck joint analysis (BK) [18]. In our preceding paper [8] our model predictions were tested through Planck 2013 and BI-CEP2 earlier data and the results were different. The MCMC results (see Tables 4 and 5) show that the quantum gravitational modification of the standard power law form for the primordial scalar spectrum, improves the fit to the data.…”

Section: Discussionmentioning

confidence: 99%

Quantum cosmology and the evolution of inflationary spectra

Kamenshchik¹,

Tronconi²,

Venturi³

2016

Phys. Rev. D

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We illustrate how it is possible to calculate the quantum gravitational effects on the spectra of primordial scalar/tensor perturbations starting from the canonical, Wheeler-De Witt, approach to quantum cosmology. The composite matter-gravity system is analysed through a Born-Oppenheimer approach in which gravitation is associated with the heavy degrees of freedom and matter (here represented by a scalar field) with the light ones. Once the independent degrees of freedom are identified the system is canonically quantised. The differential equation governing the dynamics of the primordial spectra with its quantum-gravitational corrections is then obtained and is applied to diverse inflationary evolutions. Finally, the analytical results are compared to observations through a Monte Carlo Markov Chain technique and an estimate of the free parameters of our approach is finally presented and the results obtained are compared with previous ones. * Alexander.Kamenshchik@bo.infn.it † Alessandro.Tronconi@bo.infn.it ‡ Giovanni.Venturi@bo.infn.it

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“…lv See [240,241] also for a study of inflationary dynamics in the context of the mini-superspace approximation to the Wheeler-DeWitt equation where large scale power is similarly suppressed.…”

Section: Initial State Effects?mentioning

confidence: 99%

Features and new physical scales in primordial observables: Theory and observation

Chluba

Hamann

Patil

2015

Int. J. Mod. Phys. D

197

232

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June 22, 20152 All cosmological observations to date are consistent with adiabatic, Gaussian and nearly scale invariant initial conditions. These findings provide strong evidence for a particular symmetry breaking pattern in the very early universe (with a close to vanishing order parameter, ), widely accepted as conforming to the predictions of the simplest realizations of the inflationary paradigm. However, given that our observations are only privy to perturbations, in inferring something about the background that gave rise to them, it should be clear that many different underlying constructions project onto the same set of cosmological observables. Features in the primordial correlation functions, if present, would offer a unique and discriminating window onto the parent theory in which the mechanism that generated the initial conditions is embedded. In certain contexts, simple linear response theory allows us to infer new characteristic scales from the presence of features that can break the aforementioned degeneracies among different background models, and in some cases can even offer a limited spectroscopy of the heavier degrees of freedom that couple to the inflaton. In this review, we offer a pedagogical survey of the diverse, theoretically well grounded mechanisms which can imprint features into primordial correlation functions in addition to reviewing the techniques one can employ to probe observations. These observations include cosmic microwave background anisotropies and spectral distortions as well as the matter two and three point functions as inferred from large-scale structure and potentially, 21 cm surveys.

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Signatures of quantum gravity in a Born–Oppenheimer context

Cited by 41 publications

References 27 publications

Construction of quantum Dirac observables and the emergence of WKB time

Construction of quantum Dirac observables and the emergence of WKB time

Quantum cosmology and the evolution of inflationary spectra

Features and new physical scales in primordial observables: Theory and observation

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