Renormalization group scale-setting from the action—a road to modified gravity theories

Domazet, Silvije; Štefančić, Hrvoje

doi:10.1088/0264-9381/29/23/235005

Cited by 46 publications

(64 citation statements)

References 30 publications

(65 reference statements)

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“…Assuming that there is no energy-momentum flow between the gravitational and matter components of the theory, i.e. that the energy-momentum tensor T µν is separately conserved, the momentum-scale k = k(x) is determined by a set of of consistency conditions dictated by the Bianchi identities [50][51][52][53][54]. In particular, diffeomorphism invariance requires [51,53,54]…”

Section: Running Couplings and Effective Actionsmentioning

confidence: 99%

The Inflationary Mechanism in Asymptotically Safe Gravity

Platania

2019

Universe

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According to the asymptotic safety conjecture, gravity is a renormalizable quantum field theory whose continuum limit is defined by an interacting fixed point of the renormalization group flow. In these proceedings we review some implications of the existence of this nontrivial fixed point in cosmological contexts. Specifically, we discuss a toy model exemplifying how the departure from the fixed-point regime can explain the approximate scale-invariance of the power spectrum of temperature fluctuations in the cosmic microwave background. I. INTRODUCTIONPrimordial quantum fluctuations occurring in the pre-inflationary epoch have left indelible imprints which we measure today in the form of tiny temperature anisotropies, δT /T ∼ 10 −5 , in the Cosmic Microwave Background (CMB) radiation. The inflationary mechanism furnishes a simple explanation for the presence of these anisotropies [1] and it has become a paradigm in the description of the primordial evolution of the universe within the standard cosmological model.The spectrum of the CMB reproduces an almost perfect black-body radiation at an average temperature T ∼ 2.7K. The distribution of temperature fluctuations in the CMB is described by the power spectra of scalar and tensorial perturbations. These spectra are essentially characterized by two parameters: the spectral index n s , giving information on the scale dependence of the power spectrum of scalar fluctuations, and the tensor-to-scalar ratio r, measuring the suppression of tensorial perturbations against the scalar ones. The values of the spectral index n s and tensorto-scalar ratio r can be obtained from the observational data. In particular, the most recent observations to date [2] constrain the spectral index to be n s = 0.9649 ± 0.0042 at 68% CF, and limit the tensor-to-scalar ratio to values r < 0.064. Note that, although the scalar power spectrum is almost scale invariant, perfect scale invariance, corresponding to n s = 1, seems to be excluded.The extraordinary predictive power of the inflationary scenario, combined with the current limits on the determination of r, makes it difficult to distinguish between different models of cosmic inflation [3]. The simplest inflationary model capable of explaining the current observational data is * a.platania@thphys.uni-heidelberg.de arXiv:1908.03897v1 [gr-qc]

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Section: Running Couplings and Effective Actionsmentioning

confidence: 99%

The Inflationary Mechanism in Asymptotically Safe Gravity

Platania

2019

Universe

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“…which can thus be understood as variational scale setting procedure [62][63][64][65][66]. The combination of (27) with the above equations of motion guarantees the conservation of the stress energy tensors.…”

Section: Scale Dependent Couplings and Scale Settingmentioning

confidence: 99%

Scale-dependent three-dimensional charged black holes in linear and non-linear electrodynamics

et al. 2017

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In the present work we study the scale dependence at the level of the effective action of charged black holes in Einstein-Maxwell as well as in Einstein-powerMaxwell theories in (2 + 1)-dimensional spacetimes without a cosmological constant. We allow for scale dependence of the gravitational and electromagnetic couplings, and we solve the corresponding generalized field equations imposing the null energy condition. Certain properties, such as horizon structure and thermodynamics, are discussed in detail.

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“…[49], some consider the RG improved equations (e.g., [42,[72][73][74]), in which the coupling constants are promoted to running ones at the level of the field equations. In the case of RGGR, this promotion is done at the level of the action, and hence it is a case of RG improved action (see e.g., [49,[75][76][77][78][79]). Moreover, it has an action that leads to all the field equations [47].…”

Section: A a Brief Review On Rggr And A Larger Class Of Theoriesmentioning

confidence: 99%

Will-Nordtvedt PPN formalism applied to renormalization group extensions of general relativity

et al. 2017

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We apply the full Will-Nordtvedt version of the Parameterized Post-Newtonian (PPN) formalism to a class of General Relativity extensions that are based on nontrivial renormalization group (RG) effects at large scales. We focus on a class of models in which the gravitational coupling constant G is correlated with the Newtonian potential. A previous PPN analysis considered a specific realization of the RG effects, and only within the Eddington-Robertson-Schiff version of the PPN formalism, which is a less complete and robust PPN formulation. Here we find stronger, more precise bounds, and with less assumptions. We also consider the External Potential Effect (EPE), which is an effect that is intrinsic to this framework and depends on the system environment (it has some qualitative similarities to the screening mechanisms of modified gravity theories). We find a single particular RG realization that is not affected by the EPE. Some physical systems have been pointed out as candidates for measuring the possible RG effects in gravity at large scales, for any of them the Solar System bounds need to be considered.

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Renormalization group scale-setting from the action—a road to modified gravity theories

Cited by 46 publications

References 30 publications

The Inflationary Mechanism in Asymptotically Safe Gravity

The Inflationary Mechanism in Asymptotically Safe Gravity

Scale-dependent three-dimensional charged black holes in linear and non-linear electrodynamics

Will-Nordtvedt PPN formalism applied to renormalization group extensions of general relativity

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