Matter matters in asymptotically safe quantum gravity

Donà, Pietro; Eichhorn, Astrid; Percacci, Roberto

doi:10.1103/physrevd.89.084035

Cited by 247 publications

(452 citation statements)

References 133 publications

(259 reference statements)

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“…In addition to the scalar matter fields underlying our considerations up to this point we can also bring massless free Dirac fermions into play and couple them (minimally) to the dynamical metric by adding a corresponding term to the matter action (1.3). The contribution of each of such fermions to the β-function of Newton's constant in d = 2 + ε is the same as for a scalar field [90,91], that is, fermions and scalars enter the central charge in the same way. Hence, in all above equations for β-functions and central charges we may identify N with 11) where N S and N F denote the number of real scalars and Dirac fermions, respectively.…”

Section: Jhep02(2016)167mentioning

confidence: 67%

The unitary conformal field theory behind 2D Asymptotic Safety

Nink

Reuter

2016

J. High Energ. Phys.

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Being interested in the compatibility of Asymptotic Safety with Hilbert space positivity (unitarity), we consider a local truncation of the functional RG flow which describes quantum gravity in d > 2 dimensions and construct its limit of exactly two dimensions. We find that in this limit the flow displays a nontrivial fixed point whose effective average action is a non-local functional of the metric. Its pure gravity sector is shown to correspond to a unitary conformal field theory with positive central charge c = 25. Representing the fixed point CFT by a Liouville theory in the conformal gauge, we investigate its general properties and their implications for the Asymptotic Safety program. In particular, we discuss its field parametrization dependence and argue that there might exist more than one universality class of metric gravity theories in two dimensions. Furthermore, studying the gravitational dressing in 2D asymptotically safe gravity coupled to conformal matter we uncover a mechanism which leads to a complete quenching of the a priori expected Knizhnik-Polyakov-Zamolodchikov (KPZ) scaling. A possible connection of this prediction to Monte Carlo results obtained in the discrete approach to 2D quantum gravity based upon causal dynamical triangulations is mentioned. Similarities of the fixed point theory to, and differences from, non-critical string theory are also described. On the technical side, we provide a detailed analysis of an intriguing connection between the Einstein-Hilbert action in d > 2 dimensions and Polyakov's induced gravity action in two dimensions.

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Section: Jhep02(2016)167mentioning

confidence: 67%

The unitary conformal field theory behind 2D Asymptotic Safety

Nink

Reuter

2016

J. High Energ. Phys.

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“…Here we make use of structural similarities between quantum Einstein gravity and unimodular gravity at the level of the background couplings, which imply that the matter contributions to the running of the background Newton coupling in unimodular gravity agree with [94,95]. We find bounds on the number of allowed scalars and fermions, at a fixed number of Abelian vector bosons.…”

Section: Discussionmentioning

confidence: 99%

“…For instance, it is no longer true when wave-function renormalizations for the matter fields are included, as these are derived from different graviton-matter-vertices. We can thus take the matter contributions from [94,95] and add these to the beta function for the background Newton coupling, where we use the n = 1 truncation and identify a 1 = −1/(16πG) and subsequently expand to second order in G. We then have that 1) where N V is the number of abelian vector fields, N D the number of Dirac fields, N S the number of real scalars and N RS the number of Rarita-Schwinger fields with spin 3/2. Herein a type-II cutoff (nomenclature as in [29,30]) has been used for the matter fields, as it is required for the proper treatment of fermions [96].…”

Section: Toward the Real World: Adding Mattermentioning

confidence: 99%

The Renormalization Group flow of unimodular f(R) gravity

Eichhorn

2015

J. High Energ. Phys.

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125

101

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Unimodular gravity is classically equivalent to General Relativity. This equivalence extends to actions which are functions of the curvature scalar. At the quantum level, the dynamics could differ. Most importantly, the cosmological constant is not a coupling in the unimodular action, providing a new vantage point from which to address the cosmological constant fine-tuning problem. Here, a quantum theory based on the asymptotic safety scenario is studied, and evidence for an interacting fixed point in unimodular f (R) gravity is found. We study the fixed point and its properties, and also discuss the compatibility of unimodular asymptotic safety with dynamical matter, finding evidence for its compatibility with the matter degrees of freedom of the Standard Model.

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“…As argued in [61] the presence of matter field could change the sign of Λ depending on the number of Dirac, scalar and vector fields. We hope to address this issue in a future investigation.…”

Section: Inflation Dynamics and Primordial Spectrummentioning

confidence: 99%

Asymptotically safe inflation from quadratic gravity

Platania¹,

Bonanno²

2016

Proceedings of Proceedings of the Corfu Summer Institute 2015 — PoS(CORFU2015)

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Asymptotically Safe theories of gravity have recently received much attention. In this work we discuss a class of inflationary models derived from quantum-gravity modification of quadratic gravity according to the induced scaling around the non-Gaussian fixed point at very high energies. It is argued that the presence of a three dimensional ultraviolet critical surface generates operators of non-integer power of the type R 2−θ/2 in the effective Lagrangian, where θ > 0 is a critical exponent. The requirement of a successful inflationary model in agreement with the recent Planck 2015 data puts important constraints on the strenght of this new type of couplings.

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Matter matters in asymptotically safe quantum gravity

Cited by 247 publications

References 133 publications

The unitary conformal field theory behind 2D Asymptotic Safety

The unitary conformal field theory behind 2D Asymptotic Safety

The Renormalization Group flow of unimodular f(R) gravity

Asymptotically safe inflation from quadratic gravity

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