Impact of topology in foliated quantum Einstein gravity

We study the asymptotic safety conjecture for quantum gravity in the presence of matter fields. A general line of reasoning is put forward explaining why gravitons dominate the high-energy behavior, largely independently of the matter fields as long as these remain sufficiently weakly coupled. Our considerations are put to work for gravity coupled to Yang-Mills theories with the help of the functional renormalization group. In an expansion about flat backgrounds, explicit results for beta functions, fixed points, universal exponents, and scaling solutions are given in systematic approximations exploiting running propagators, vertices, and background couplings. Invariably, we find that the gauge coupling becomes asymptotically free while the gravitational sector becomes asymptotically safe. The dependence on matter field multiplicities is weak. We also explain how the scheme dependence, which is more pronounced, can be handled without changing the physics. Our findings offer a new interpretation of many earlier results, which is explained in detail. The results generalize to theories with minimally coupled scalar and fermionic matter. Some implications for the ultraviolet closure of the Standard Model or its extensions are given.

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“…For small momenta, η a;h changes sign for μ → −1. Again it can be shown that this does not happen for regulators with (38).…”

Section: B Gravity Supports Asymptotic Freedommentioning

confidence: 95%

“…For these momenta, the three-point function diagrams effectively satisfy (38), and the anomalous dimension η a;h ðp 2 Þ carries the information about the graviton contribution of the beta function of the background coupling.…”

Section: A Background Observablesmentioning

confidence: 99%

Asymptotic safety of gravity with matter

et al. 2018

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“…In the next sections, we will discuss the modifications to the mass-radius relation, maximal mass, and Buchdahl limit induced by the modified TOV equation (30).…”

Section: Quantum-improved Tov Equationmentioning

confidence: 99%

“…The effective energy density q reduces to the classical proper energy density in the limit ξ → 0, as expected. The expression (33) for the effective proper energy density affects both the continuity equation (24) and the TOV equation (30) and is the only input needed to embed the scale-dependence of the running Newton coupling into the dynamics of the system.…”

Section: Mass-radius Relation For Polytropic Quantum-improved Neutmentioning

confidence: 99%

Gravitational antiscreening in stellar interiors

Bonanno

Casadio

Platania

2020

J. Cosmol. Astropart. Phys.

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A new class of relativistic stellar structure equations which include the antiscreening effect of the gravitational interaction is presented. Significant modifications in the mass-radius relation for neutron stars can be expected if the running of the Newton coupling due to quantum gravity occurs at low energies. A new Buchdahl limit is derived and its physical implications are discussed. In particular sub-Planckian self-gravitating objects with arbitrarily small radii are possible.

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“…As a consequence the effective average action agrees with the standard effective action in this limit, lim k→0 Γ k ≡ Γ. Finally, the framework turns out to be sufficiently flexible to probe settings where different classes of metric fluctuations are admitted by either implementing a linear split [13], an exponential split [93,94], or an ADM split [95][96][97] of the gravitational degrees of freedom. Throughout this work, we will implement a linear split, decomposing the physical metric g µν into a fixed background metricḡ µν and fluctuations h µν according to…”

Section: Jhep12(2017)121mentioning

confidence: 52%

On avoiding Ostrogradski instabilities within Asymptotic Safety

Becker

Ripken

Saueressig

2017

J. High Energ. Phys.

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We study the renormalization group flow of gravity coupled to scalar matter using functional renormalization group techniques. The novel feature is the inclusion of higher-derivative terms in the scalar propagator. Such terms give rise to Ostrogradski ghosts which signal an instability of the system and are therefore dangerous for the consistency of the theory. Since it is expected that such terms are generated dynamically by the renormalization group flow they provide a potential threat when constructing a theory of quantum gravity based on Asymptotic Safety. Our work then establishes the following picture: upon incorporating higher-derivative terms in the scalar propagator the flow of the gravity-matter system possesses a fixed point structure suitable for Asymptotic Safety. This structure includes an interacting renormalization group fixed point where the Ostrogradski ghosts acquire an infinite mass and decouple from the system. Tracing the flow towards the infrared it is found that there is a subset of complete renormalization group trajectories which lead to stable renormalized propagators. This subset is in one-to-one correspondence to the complete renormalization group trajectories obtained in computations which do not keep track of the higher-derivative terms. Thus our asymptotically safe gravity-matter systems are not haunted by Ostrogradski ghosts.

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Impact of topology in foliated quantum Einstein gravity

Cited by 64 publications

References 144 publications

Asymptotic safety of gravity with matter

Asymptotic safety of gravity with matter

Gravitational antiscreening in stellar interiors

On avoiding Ostrogradski instabilities within Asymptotic Safety

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