Responses from the authors to comments of anonymous Referee #1 - bg-2019-71

Wetterich, Sebastian

doi:10.5194/bg-2019-71-ac1

Cited by 4 publications

(6 citation statements)

References 1 publication

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“…A fundamental description, i.e., valid up to arbitrarily short distances, of the building blocks of nature in the quantum field theory framework requires theory to be either asymptotically free or safe. Both cases provide a framework for an ultraviolet completion of effective field theories, in which an enhanced symmetry, quantum scale symmetry [17], rules the microscopic dynamics. Scale-symmetry is a consequence of vanishing interactions in the case of 2 Analogous considerations hold in settings beyond the Standard Model.…”

Section: Introductionmentioning

confidence: 99%

A link that matters: towards phenomenological tests of unimodular asymptotic safety

Brito

Eichhorn

Pereira

2019

J. High Energ. Phys.

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Constraining quantum gravity from observations is a challenge. We expand on the idea that the interplay of quantum gravity with matter could be key to meeting this challenge.Thus, we set out to confront different potential candidates for quantum gravity -unimodular asymptotic safety, Weyl-squared gravity and asymptotically safe gravity -with constraints arising from demanding an ultraviolet complete Standard Model. Specifically, we show that within approximations, demanding that quantum gravity solves the Landau-pole problems in Abelian gauge couplings and Yukawa couplings strongly constrains the viable gravitational parameter space. In the case of Weyl-squared gravity with a dimensionless gravitational coupling, we also investigate whether the gravitational contribution to beta functions in the matter sector calculated from functional Renormalization Group techniques is universal, by studying the dependence on the regulator, metric field parameterization and choice of gauge. I. INTRODUCTIONObservational constraints on quantum gravity are hard to come by. Based on a simple dimensional argument, one typically expects a power-law suppression of quantum-gravity effects 1 with (E/M Pl ) # , with E being the energy scale relevant for experiments, M Pl being the Planck mass and # > 0. Nevertheless, mathematical and internal consistency are not the only conditions that could * Electronic address: gpbrito@cbpf.br † Electronic address: eichhorn@sdu.dk ‡ Electronic address: adpjunior@id.uff.br 1 In the presence of a second "meso"-scale, as hinted at by some quantum-gravity approaches, e.g., [1], this situation can change.

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Section: Introductionmentioning

confidence: 99%

A link that matters: towards phenomenological tests of unimodular asymptotic safety

Brito

Eichhorn

Pereira

2019

J. High Energ. Phys.

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“…Potential cosmological implications are reviewed in [54] and possible consequences for black-hole physics explored, e.g., in [55][56][57][58][59][60][61][62][63], see [64][65][66] for recent reviews. See [67] for an introduction to quantum scale symmetry and [68] for a review of asymptotic safety and underlying mechanisms in various models.…”

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confidence: 99%

Asymptotic safety, string theory and the weak gravity conjecture

et al. 2019

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We propose a scenario with string theory in the deep ultraviolet, an intermediate asymptotically safe scaling regime for gravity and matter, and the Standard Model in the infrared. This could provide a new perspective to tackle challenges of the two models: For instance, the gravitational Renormalization Group flow could connect a negative microscopic to a positive macroscopic cosmological constant, potentially rendering string theory on an anti-de Sitter background observationally viable. Further, the unitarity of a string-theoretic ultraviolet completion could be inherited by an asymptotically safe fixed point, despite the presence of higher-order interactions. We discuss necessary conditions on the scale of asymptotic safety and the string scale for our scenario to be viable. As a first test, we explore the weak-gravity conjecture in the context of asymptotically safe gravity.

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“…In the present work we use the gauge choice β = 0 and α → 0, for which a considerable simplification in the flow equations happens. As discussed in Appendix B, for this gauge choice, the σ mode in the York decomposition (11) is decoupled from the mixing with the other spin-0 scalar modes (h and ϕ -with ϕ being the quantum fluctuation of the scalar field about a fixed background configuration). It is important to emphasize, however, that beta functions are (off-shell) gauge dependent quantities, and therefore the physical conclusions should be carefully extracted from these objects.…”

Section: Computing Beta Functionsmentioning

confidence: 99%

“…In this approach, a fundamental quantum theory of gravity could be realized thanks to the existence of a non-trivial ultraviolet (UV) fixed point in the renormalization group flow. At this fixed point, the theory becomes scale invariant [11] and one is allowed to zoom in up to arbitrarily short distances without running into divergences. Being an interacting fixed point, the counting of relevant directions in theory space, i.e., the number of free parameters to be fixed by experiments is not controlled by the canonical dimensionality of the corresponding couplings.…”

Section: Introductionmentioning

confidence: 99%

On the impact of Majorana masses in gravity-matter systems

Brito

Hamada

Pereira

et al. 2019

J. High Energ. Phys.

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We investigate the Higgs-Yukawa system with Majorana masses of a fermion within asymptotically safe quantum gravity. Using the functional renormalization group method we derive the beta functions of the Majorana masses and the Yukawa coupling constant and discuss the possibility of a non-trivial fixed point for the Yukawa coupling constant. In the gravitational sector we take into account higher derivative terms such as R 2 and Rµν R µν in addition to the Einstein-Hilbert term for our truncation. For a certain value of the gravitational coupling constants and the Majorana masses, the Yukawa coupling constant has a non-trivial fixed point value and becomes an irrelevant parameter being thus a prediction of the theory. We also discuss consequences due to the Majorana mass terms to the running of the quartic coupling constant in the scalar sector. * Electronic address: gpbrito@cbpf.br † Electronic address: yhamada@physics.uoc.gr ‡ Electronic address: adpjunior@id.uff.br § Electronic address: m.yamada@thphys.uni-heidelberg.de scale k. Several subsequent works, employing more sophisticated approximations provided compelling support for the existence of such the Reuter fixed point, see, e.g., . Remarkably, the existence of the UV fixed point has shown to be preserved against the introduction of Standard Model (SM) matter degrees of freedom, hinting to a fundamental theory of quantum gravity which is compatible with the observed SM particles, see [9,. Moreover, many different works have provided evidence for a saturation on the number of relevant directions associated to the Reuter fixed point, ensuring thus, predictivity [30,31,35,38,42,44,45,49,50,67,[79][80][81]. This underpins the quest for a quantum theory of gravity by using continuum quantum field theory methods.Within the asymptotic safety scenario, coupling matter degrees of freedom to (quantum) gravity is straightforward. This allows for a rich interplay between the effects of matter fluctuations into gravitational running couplings and the reverse. In particular, this opens the possibility to test whether quantum gravitational effects allow for the resolution of long-standing problems as, e.g., the triviality problem in the SM, see [82][83][84]. Having a fundamental theory of gravity and matter valid up to arbitrarily short distances also leads to an enhancement of predictivity. In fact, the fixed point structure as well as the assumption that the SM holds up all the way until the Planck scale leads to a prediction of the Higgs mass to be m H = 126 GeV for the top quark mass m t = 171 GeV, see [78,85]. This happens thanks to its quantum-gravity induced irrelevance, being thus a prediction and not a free parameter of the theory. Recent works [84,86,87] have managed to successfully explain observed quantities in the low energy regimes by assuming the existence of the asymptotically safe fixed point for gravity-matter systems. Furthermore, asymptotically safe quantum gravity might be able to provide solutions for important problems in both particle physics and c...

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Responses from the authors to comments of anonymous Referee #1 - bg-2019-71

Cited by 4 publications

References 1 publication

A link that matters: towards phenomenological tests of unimodular asymptotic safety

A link that matters: towards phenomenological tests of unimodular asymptotic safety

Asymptotic safety, string theory and the weak gravity conjecture

On the impact of Majorana masses in gravity-matter systems

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