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Loop-and-allied QG bibliography

  1. Jan 7, 2017 #2481
    Quantum gravity and Standard-Model-like fermions
    Astrid Eichhorn, Stefan Lippoldt
    (Submitted on 17 Nov 2016)
    We discover that chiral symmetry does not act as an infrared attractor of the renormalization group flow under the impact of quantum gravity fluctuations. Thus, observationally viable quantum gravity models must respect chiral symmetry. In our truncation, asymptotically safe gravity does, as a chiral fixed point exists. A second non-chiral fixed point with massive fermions provides a template for models with dark matter. This fixed point disappears for more than 10 fermions, suggesting that an asymptotically safe ultraviolet completion for the standard model plus gravity enforces chiral symmetry.
    Comments: 6 pages, 2 figures
    Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)
    Cite as: arXiv:1611.05878 [gr-qc]
    Quantum-gravity effects on a Higgs-Yukawa model
    Astrid Eichhorn, Aaron Held, Jan M. Pawlowski
    (Submitted on 7 Apr 2016 (v1), last revised 13 Sep 2016 (this version, v2))
    A phenomenologically viable theory of quantum gravity must accommodate all observed matter degrees of freedom and their properties. Here, we explore whether a toy model of the Higgs-Yukawa sector of the Standard Model is compatible with asymptotically safe quantum gravity. We discuss the phenomenological implications of our result in the context of the Standard Model. We analyze the quantum scaling dimension of the system, and find an irrelevant Yukawa coupling at a joint gravity-matter fixed point. Further, we explore the impact of gravity-induced couplings between scalars and fermions, which are non-vanishing in asymptotically safe gravity.
    Comments: 13 pages + appendix, 10 figures, simplified basis for induced couplings
    Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
    Journal reference: Phys. Rev. D 94, 104027 (2016)
    DOI: 10.1103/PhysRevD.94.104027
    Cite as: arXiv:1604.02041 [hep-th]
    (or arXiv:1604.02041v2 [hep-th] for this version)
     
  2. Jan 7, 2017 #2482
    Quantum gravity on foliated spacetime - asymptotically safe and sound
    Jorn Biemans, Alessia Platania, Frank Saueressig
    (Submitted on 15 Sep 2016 (v1), last revised 17 Oct 2016 (this version, v2))
    Asymptotic Safety provides a mechanism for constructing a consistent and predictive quantum theory of gravity valid on all length scales. Its key ingredient is a non-Gaussian fixed point of the gravitational renormalization group flow which controls the scaling of couplings and correlation functions at high energy. In this work we use a functional renormalization group equation adapted to the ADM-formalism for evaluating the gravitational renormalization group flow on a cosmological Friedmann-Robertson-Walker background. Besides possessing the UV-non-Gaussian fixed point characteristic for Asymptotic Safety the setting exhibits a second non-Gaussian fixed point with a positive Newton's constant and real critical exponents. The new fixed point alters the phase diagram in such a way that all renormalization group trajectories connected to classical general relativity are well-defined on all length scales. In particular a positive cosmological constant is dynamically driven to zero in the deep infrared. Moreover, the scaling dimensions associated with the universality classes emerging within the causal setting exhibit qualitative agreement with results found within the ϵ-expansion around two dimensions, Monte Carlo simulations based on Lattice Quantum Gravity, and the discretized Wheeler-deWitt equation.
    Comments: 7 pages, 3 figures. Conclusions slightly modified
    Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
    Cite as: arXiv:1609.04813 [hep-th]
    (or arXiv:1609.04813v2 [hep-th] for this version)
     
  3. Jan 10, 2017 #2483

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    https://arxiv.org/abs/1701.02282
    Some Clarifications on the Duration of Inflation in Loop Quantum Cosmology
    Boris Bolliet, Aurélien Barrau, Killian Martineau, Flora Moulin
    (Submitted on 9 Jan 2017)
    The prediction of a phase of inflation whose number of e-folds is constrained is an important feature of loop quantum cosmology. This work aims at giving some elementary clarifications on the role of the different hypotheses leading to this conclusion. We show that the duration of inflation does not depend significantly on the modified background dynamics in the quantum regime.

    https://arxiv.org/abs/1701.02037
    (3+1)-dimensional topological phases and self-dual quantum geometries encoded on Heegard surfaces
    Bianca Dittrich
    (Submitted on 8 Jan 2017)
    We apply the recently suggested strategy to lift state spaces and operators for (2+1)-dimensional topological quantum field theories to state spaces and operators for a (3+1)-dimensional TQFT with defects. We start from the (2+1)-dimensional Turaev-Viro theory and obtain the state space for the Crane-Yetter model with line defects.
    This work has important applications for quantum gravity as well as the theory of topological phases in (3+1) dimensions. It provides a self-dual quantum geometry realization based on a vacuum state peaked on a homogeneously curved geometry. The state spaces and operators we construct here provide also an improved version of the Walker-Wang model, and simplify its analysis considerably.
    We in particular show that the fusion bases of the (2+1)-dimensional theory lead to a rich set of bases for the (3+1)-dimensional theory. This includes a quantum deformed spin network basis, which in a loop quantum gravity context diagonalizes spatial geometry operators. We also obtain a dual curvature basis, that diagonalizes the Walker-Wang Hamiltonian.
    Furthermore, the construction presented here can be generalized to provide state spaces for the recently introduced dichromatic four--dimensional manifold invariants.
     
  4. Jan 11, 2017 #2484

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    https://arxiv.org/abs/1701.02311
    Hypercuboidal renormalization in spin foam quantum gravity
    Benjamin Bahr, Sebastian Steinhaus
    (Submitted on 9 Jan 2017)
    In this article we apply background-independent renormalization group methods to spin foam quantum gravity. It is aimed at extending and elucidating the analysis of a companion letter, in which the existence of a fixed point in the truncated RG flow for the model was reported. Here we repeat the analysis with various modifications, and find that both qualitative and quantitative features of the fixed point are robust in this setting. We also go into details about the various approximation schemes employed in the analysis.

    https://arxiv.org/abs/1701.02439
    Discretization of 3d gravity in different polarizations
    Maïté Dupuis, Laurent Freidel, Florian Girelli
    (Submitted on 10 Jan 2017)
    We study the discretization of 3d gravity with Λ=0 following the loop quantum gravity framework. In the process, we realize that different choices of polarization are possible. This allows to introduce a new discretization based on the triad as opposed to the connection as in the standard loop quantum gravity framework. We also identify the classical non-trivial symmetries of discrete gravity, namely the Drinfeld double, given in terms of momentum maps. Another choice of polarization is given by the Chern-Simons formulation of gravity. Our framework also provides a new discretization scheme of Chern-Simons, which keeps track of the link between the continuum variables and the discrete ones. We show how the Poisson bracket we recover between the Chern-Simons holonomies allows to recover the Goldman bracket. There is also a transparent link between the discrete Chern-Simons formulation and the discretization of gravity based on the connection (loop gravity) or triad variables (dual loop gravity).
     
  5. Jan 11, 2017 #2485

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    https://arxiv.org/abs/1701.03029
    Flowing to the continuum in discrete tensor models for quantum gravity
    Astrid Eichhorn, Tim Koslowski
    (Submitted on 11 Jan 2017)
    Tensor models provide a way to access the path-integral for discretized quantum gravity in d dimensions. As in the case of matrix models for two-dimensional quantum gravity, the continuum limit can be related to a Renormalization Group fixed point in a setup where the tensor size N serves as the Renormalization Group scale. We develop functional Renormalization Group tools for tensor models with a main focus on a rank-3 model for three-dimensional quantum gravity. We rediscover the double-scaling limit and provide an estimate for the scaling exponent. Moreover, we identify two additional fixed points with a second relevant direction in a truncation of the Renormalization Group flow. The new relevant direction might hint at the presence of additional degrees of freedom in the corresponding continuum limit.
     
  6. Jan 14, 2017 at 12:46 AM #2486
    Naturalness of asymptotically safe Higgs
    Giulio Maria Pelaggi, Francesco Sannino, Alessandro Strumia, Elena Vigiani
    (Submitted on 5 Jan 2017)
    We introduce a model that contains a Higgs-like scalar with gauge, Yukawa and quartic interactions that enter a perturbative asymptotically safe regime at energies above a scale Λ. The model serves as a concrete example to test whether scalars masses unavoidably receive quantum correction of order Λ. The answer is that scalars can be naturally lighter. Although we do not have an answer to whether the Standard Model hypercharge coupling growth towards a Landau pole around Λ∼1040 GeV can be tamed by non-perturbative asymptotic safety, our toy-SM shows that such a possibility is worth exploring. In fact, if successful, it might also offer an explanation for the unbearable lightness of the Higgs.
    Comments: 16 pages
    Subjects: High Energy Physics - Phenomenology (hep-ph)
    Report number: CERN-PH-TH-2017-001, CP3-Origins-2017-001, IFUP-TH/2017
    Cite as: arXiv:1701.01453 [hep-ph]
    (or arXiv:1701.01453v1 [hep-ph] for this versio
     
  7. Jan 16, 2017 at 12:14 AM #2487
    Detailed investigation of the duration of inflation in loop quantum cosmology for a Bianchi-I universe with different inflaton potentials and initial conditions
    Killian Martineau, Aurélien Barrau, Susanne Schander
    (Submitted on 10 Jan 2017)
    There is a wide consensus on the correct dynamics of the background in loop quantum cosmology. In this article we make a systematic investigation of the duration of inflation by varying what we think to be the most important "unknowns" of the model: the way to set initial conditions, the amount of shear at the bounce and the shape of the inflaton potential.
    Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)
    Cite as: arXiv:1701.02703 [gr-qc]
     
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