Constraints on discrete global symmetries in quantum gravity

Ali, Passant; Eichhorn, Astrid; Pauly, Martin; Scherer, Michael M.

doi:10.1007/jhep05(2021)036

Cited by 15 publications

(8 citation statements)

References 97 publications

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“…The situation is unique in asymptotically safe gravity-matter models, where strong indications for a high predictive power exist: the low-energy values of various couplings could either be bounded from above or be fixed precisely [11][12][13][14][15], an argument for the preference of four spacetime dimensions has been derived based on the gravity-matter interplay [16], upper and lower bounds on the number of light fermions may exist [17][18][19] and certain discrete symmetries may be prohibited [20].…”

Section: Jhep11(2021)110mentioning

confidence: 99%

The weak-gravity bound and the need for spin in asymptotically safe matter-gravity models

Brito

Eichhorn

Santos

2021

J. High Energ. Phys.

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We discover a weak-gravity bound in scalar-gravity systems in the asymptotic-safety paradigm. The weak-gravity bound arises in these systems under the approximations we make, when gravitational fluctuations exceed a critical strength. Beyond this critical strength, gravitational fluctuations can generate complex fixed-point values in higher-order scalar interactions. Asymptotic safety can thus only be realized at sufficiently weak gravitational interactions. We find that within truncations of the matter-gravity dynamics, the fixed point lies beyond the critical strength, unless spinning matter, i.e., fermions and vectors, is also included in the model.

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Section: Jhep11(2021)110mentioning

confidence: 99%

The weak-gravity bound and the need for spin in asymptotically safe matter-gravity models

Brito

Eichhorn

Santos

2021

J. High Energ. Phys.

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“…This perspective has been investigated within Asymptotic Safety for a long time, see [136][137][138][139]. For the interplay between gravity and scalar fields within the asymptotic safety scenario, we refer to [140][141][142][143][144][145][146][147][148][149][150][151][152][153][154][155][156][157]. In the case of gravity-fermion systems, see [158][159][160][161][162][163][164][165][166].…”

Section: Introductionmentioning

confidence: 99%

Scalar-tensor theories within Asymptotic Safety

Laporte

Pereira

Saueressig

et al. 2021

J. High Energ. Phys.

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Asymptotic Safety provides an elegant mechanism for obtaining a consistent high-energy completion of gravity and gravity-matter systems. Following the initial idea by Steven Weinberg, the construction builds on an interacting fixed point of the theories renormalization group (RG) flow. In this work we use the Wetterich equation for the effective average action to investigate the RG flow of gravity supplemented by a real scalar field. We give a non-perturbative proof that the subspace of interactions respecting the global shift-symmetry of the scalar kinetic term is closed under RG transformations. Subsequently, we compute the beta functions in an approximation comprising the Einstein-Hilbert action supplemented by the shift-symmetric quartic scalar self-interaction and the two lowest order shift-symmetric interactions coupling scalar-bilinears to the spacetime curvature. The computation utilizes the background field method with an arbitrary background, demonstrating that the results are manifestly background independent. Our beta functions exhibit an interacting fixed point suitable for Asymptotic Safety, where all matter interactions are non-vanishing. The presence of this fixed point is rooted in the interplay of the matter couplings which our work tracks for the first time. The relation of our findings with previous results in the literature is discussed in detail and we conclude with a brief outlook on potential phenomenological applications.

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“…Secondly, the non-minimal interaction explicitly breaks chiral symmetry, as it provides a fermion mass set by the spacetime curvature. Thus the analysis has a natural connection to interesting questions including the existence of light chiral fermions [103] and the role of global symmetries within the asymptotic safety program [119]. While the effect of the non-minimal coupling has already been explored in [61], our work (and its companion [80]) is the first where the role of the explicit symmetry breaking terms is studied in a non-flat background.…”

Section: Discussionmentioning

confidence: 94%

Asymptotically Safe Gravity-Fermion systems on curved backgrounds

Daas

Oosters

Saueressig

et al. 2021

Preprint

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We set up a consistent background field formalism for studying the renormalization group (RG) flow of gravity coupled to N f Dirac fermions on maximally symmetric backgrounds. Based on Wetterich's equation we perform a detailed study of the resulting fixed point structure in a projection including the Einstein-Hilbert action, the fermion anomalous dimension, and a specific coupling of the fermion bilinears to the spacetime curvature. The latter constitutes a mass-type term which breaks chiral symmetry explicitly. Our analysis identifies two infinite families of interacting RG fixed points which are viable candidates to provide a high-energy completion through the asymptotic safety mechanism. The fixed points exist for all values of N f outside of a small window situated at low values N f and become weakly coupled in the large N f -limit. Symmetry-wise, they correspond to "quasi-chiral" and "non-chiral" fixed points. The former come with enhanced predictive power, fixing one of the couplings via the asymptotic safety condition. Moreover, the interplay of the fixed points allows for cross-overs from the non-chiral to the chiral fixed point, giving a dynamical mechanism for restoring the symmetry approximately at intermediate scales. Our discussion of chiral symmetry breaking effects provides strong indications that the topology of spacetime plays a crucial role when analyzing whether quantum gravity admits light chiral fermions.

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Constraints on discrete global symmetries in quantum gravity

Cited by 15 publications

References 97 publications

The weak-gravity bound and the need for spin in asymptotically safe matter-gravity models

The weak-gravity bound and the need for spin in asymptotically safe matter-gravity models

Scalar-tensor theories within Asymptotic Safety

Asymptotically Safe Gravity-Fermion systems on curved backgrounds

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