On the running of the gravitational constant

Anber, Mohamed M.; Donoghue, John F.

doi:10.48550/arxiv.1111.2875

Cited by 10 publications

(14 citation statements)

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“…First, one should notice that even though G is an essential coupling in UG, this still does not mean that its running can be directly translated in a physical prediction: at the perturbative level, G gets renormalized by quadratic divergences, and this means that the running is not universal, as discussed in [42]. And in fact we found that the beta function still depends (even at one-loop, with the exception of 2 + ǫ dimensions) on the choice of cutoff.…”

Section: Discussionmentioning

confidence: 99%

Essential nature of Newton’s constant in unimodular gravity

Benedetti

2016

Gen Relativ Gravit

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We point out that in unimodular gravity Newton's constant is an essential coupling, i.e. it is independent of field redefinitions. We illustrate the consequences of this fact by a calculation in a standard simple approximation, showing that in this case the renormalization group flow of Newton's constant is gauge and parametrization independent.Unimodular gravity is a theory of gravitation in which the metric determinant is a fixed nondynamical density. Despite being almost as old as general relativity [1], and classically equivalent to it, unimodular gravity has never reached the popularity of the standard formulation. Nevertheless, it is from time to time retrieved by different authors (e.g. [2,3,4,5,6,7,8,9]) for a number of attractive features. Most notably, in unimodular gravity the cosmological constant appears as an integration constant rather than as a coupling in the action, and therefore it is not subject to quantum corrections. Such feature is of course attractive in the context of the cosmological constant problem, although by itself it is not a full solution [6]. The unimodularity constraint has also been argued to solve the problem of time [3], but that is also not free from difficulties [10]. At a more technical level, it can help us in several ways, for example, by recasting the action in polynomial form [2], or by getting rid of some ambiguities in the path integral measure (the DeWitt supermetric is trivially independent of the C-ambiguity).Ultimately, despite the several advantages that unimodular gravity (UG) has compared to general relativity (GR), the main big problems remain open also in this formulation, and in particular as a quantum theory UG is equally non-renormalizable as GR. Whether these two formulations of the classical theory both admit a UV completion in the quantum domain, and whether these would be equivalent as well, is an open question, and it will probably be so as long the challenge of quantizing gravity remains open. Preliminary calculations by Eichhorn [11,12] suggest that unimodular gravity might have a UV completion in the form of an asymptotic safety scenario [13,14], just like more extensive calculations have indicated for non-unimodular gravity (for a review up to 2012 see [15], for more recent results see [16,17,18] and references therein). In fact, from the point of view of a standard field theoretic quantization, the unimodularity constraint might be seen just as a (partial) gauge-fixing of the non-unimodular theory, as done recently in [19], and therefore one might expect equivalence between the two formulations. However, one should notice that when implementing the unimodularity condition as a gauge-fixing, the usual Faddev-Popov ghosts need to be included as well, whereas they are not needed if the restriction is part of the fundamental definition of the theory. We will discuss this point more explicitly in the following.In this note, we want to stress some features of unimodular gravity that make it appealing from the point of view of the renormalization group...

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Section: Discussionmentioning

confidence: 99%

Essential nature of Newton’s constant in unimodular gravity

Benedetti

2016

Gen Relativ Gravit

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“…β ∼ GΛ 2 . Papers trying to clarify this muddle include [36,37,38,39]. My treatment here most naturally follows the ones of my collaborators and myself [36,37] In renormalizable field theories, the use of a running coupling is both useful and universal.…”

Section: Gravitational Corrections and Running Coupling Constantsmentioning

confidence: 99%

“…Papers trying to clarify this muddle include [36,37,38,39]. My treatment here most naturally follows the ones of my collaborators and myself [36,37] In renormalizable field theories, the use of a running coupling is both useful and universal. It is useful because it sums up a set of quantum corrections which potentially could have large logarithmic factors.…”

Section: Gravitational Corrections and Running Coupling Constantsmentioning

confidence: 99%

The effective field theory treatment of quantum gravity

Donoghue

2012

Preprint

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This is a pedagogical introduction to the treatment of quantum general relativity as an effective field theory. It starts with an overview of the methods of effective field theory and includes an explicit example. Quantum general relativity matches this framework and I discuss gravitational examples as well as the limits of the effective field theory. I also discuss the insights from effective field theory on the gravitational effects on running couplings in the perturbative regime.

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“…This is consistent, since the coefficient of the Ricci scalar in the effective action is not affected by the quantum corrections we have considered. Here, we have not considered the running of the Planck mass, since there are not many particles in the standard model, this would be a small effects [32,33,34]. There are however well known models which can affect significantly the value of the coefficient of the Ricci scalar.…”

Section: 21)mentioning

confidence: 99%

The horizon of the lightest black hole

Calmet

Casadio

2015

Eur. Phys. J. C

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We study the properties of the poles of the resummed graviton propagator obtained by resumming bubble matter diagrams which correct the classical graviton propagator. These poles have been previously interpreted as black holes precursors. Here, we show using the horizon wavefunction formalism that these poles indeed have properties which make them compatible with being black hole precursors. In particular, when modeled with a Breit-Wigner distribution, they have a well-defined gravitational radius. The probability that the resonance is inside its own gravitational radius, and thus that it is a black hole, is about one half. Our results confirm the interpretation of these poles as black hole precursors.

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On the running of the gravitational constant

Cited by 10 publications

References 0 publications

Essential nature of Newton’s constant in unimodular gravity

Essential nature of Newton’s constant in unimodular gravity

The effective field theory treatment of quantum gravity

The horizon of the lightest black hole

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