Fri - 01/07/22

There is no new related paper today

There is no new related paper today

Thu - 01/06/22

Towards a quantum notion of covariance in spherically symmetric loop quantum gravity

  • Authors: Rodolfo Gambini, Javier Olmedo, Jorge Pullin
  • Subjects: [‘gr-qc’]
  • Arxiv link: http://arxiv.org/abs/2201.01616v1
  • Abstract The covariance of loop quantum gravity studies of spherically symmetric space-times has recently been questioned. This is a reasonable worry, given that they are formulated in terms of slicing-dependent variables. We show explicitly that the resulting space-times, obtained from Dirac observables of the quantum theory, are covariant in the usual sense of the way – they preserve the quantum line element – for any gauge that is stationary (in the exterior, if there is a horizon). The construction depends crucially on the details of the Abelianized quantization considered, the satisfaction of the quantum constraints and the recovery of standard general relativity in the classical limit and suggests that more informal polymerization constructions of possible semi-classical approximations to the theory can indeed have covariance problems. This analysis is based on the understanding of how slicing dependent quantities as the metric arise in a quantum context in terms of parameterized observables. It has implications beyond loop quantum gravity that hold for general approaches to quantum space time theories.

On the dynamical emergence of the Turaev-Viro model in $2+1D$ quantum gravity with cosmological constant

  • Authors: Niels Gresnigt, Antonino Marciano, Emanuele Zappala
  • Subjects: [‘gr-qc’, ‘hep-th’]
  • Arxiv link: http://arxiv.org/abs/2201.01726v1
  • Abstract We show the dynamical emergence of the $SU_q(2)$ quantum group symmetry in a quantum spin foam setting, starting from a kinematical $SU(2)$ theory of $2+1D$ gravity with non-zero cosmological constant. The regularized curvature constraint drives towards the emergence, for any Wilson loop evaluated at the $SU(2)$ group element that encodes the discretization of the space-time curvature induced by the cosmological constant, of effective representations of $SU_q(2)$. The definition of the Jones-Wenzl projector allows to extend the result to any transition amplitude calculated between generic spin-network states, and finally recover in full generality the recoupling theory of $SU_q(2)$. This establishes a clear link between $2+1D$ gravity with cosmological constant and the Turaev-Viro model.

Wed - 01/05/22

There is no new related paper today

There is no new related paper today

  1. [2201.00903] - Comments on Summing over bordisms in TQFT - Anindya Banerjee, Gregory W. Moore

Tue - 01/04/22

There is no new related paper today

Simplicial Quantum Gravity

  • Authors: James B. Hartle
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); History and Philosophy of Physics (physics.hist-ph); Quantum Physics (quant-ph)
  • Arxiv link: https://arxiv.org/abs/2201.00226
  • Abstract Simplicial approximation and the ideas associated with the Regge calculus.provide a concrete way of implementing a sum over histories formulation ofquantum gravity. A four-dimensional simplicial geometry is made up of flat four-simplices joined together.A sum over simplicial geometries is a sum over thedifferent ways the simplices can be joined together with an integral over their edge lengths.Theconstruction of the simplicial Euclidean action for this approach to quantum general relativity is illustrated. The recovery of the diffeomorphism group in the continuum limit is discussed. Some possible classes of simplicial complexes with which to define a sum over topologies are described.

  1. [2201.00679] - Deciphering signatures of Bardeen black holes from the observed quasi-periodic oscillations - Indrani Banerjee

  2. [2201.00026] - From Chern-Tenenblat to Jackiw-Teitelboim via sine-Gordon - Jeff Murugan

  3. [2201.00105] - Phase transitions in Skyrme holography - Casey Cartwright, Benjamin Harms, Matthias Kaminski

  4. [2201.00562] - Q-curvature and Path Integral Complexity - Hugo A. Camargo, Pawel Caputa, Pratik Nandy

Mon - 01/03/22

Numerical analysis of the self-energy in covariant LQG

  • Authors: Pietropaolo Frisoni, Francesco Gozzini, Francesca Vidotto
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2112.14781
  • Abstract We study numerically the first order radiative corrections to the self-energy, in covariant loop quantum gravity. We employ the recently developed ‘sl2cfoam-next’ spinfoam amplitudes library, and some original numerical methods. We analyze the scaling of the divergence with the infrared cutoff, for which previous analytical estimates provided widely different lower and upper bounds. Our findings suggest that the divergence is approximately linear in the cutoff. We also investigate the role of the Barbero-Immirzi parameter in the asymptotic behavior, the dependence of the scaling on some boundary data and the expectation values of boundary operators.

Non-extensive Statistical Mechanics and the Thermodynamic Stability of FRW Universe

  • Authors: Yang Liu
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2112.15077
  • Abstract In this article, we investigate the thermodynamic stability of the FRW universe for two examples, Tsallis entropy and loop quantum gravity, by considering non-extensive statistical mechanics. The heat capacity, free energy and pressure of the universe are obtained. For the Tsallis entropy model, we obtained the constraint for $\beta$, namely, $1/2 < \beta < 2$. The free energy of a thermal equilibrium universe must be less than zero. We suggest that the reason for the accelerated expansion of the universe is not due to Tsallis entropy. Similar results are obtained for loop quantum gravity. However, since the values of $\Lambda(\gamma)$ and $q$ cannot be determined in this model, the results become more subtle than that in the Tsallis entropy model. In addition, we compare the results for the universe with those for a Schwarzschild black hole.

Numerical analysis of the self-energy in covariant LQG

  • Authors: Pietropaolo Frisoni, Francesco Gozzini, Francesca Vidotto
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2112.14781
  • Abstract We study numerically the first order radiative corrections to the self-energy, in covariant loop quantum gravity. We employ the recently developed ‘sl2cfoam-next’ spinfoam amplitudes library, and some original numerical methods. We analyze the scaling of the divergence with the infrared cutoff, for which previous analytical estimates provided widely different lower and upper bounds. Our findings suggest that the divergence is approximately linear in the cutoff. We also investigate the role of the Barbero-Immirzi parameter in the asymptotic behavior, the dependence of the scaling on some boundary data and the expectation values of boundary operators.

  1. [2112.15387] - Complex actions and causality violations: Applications to Lorentzian quantum cosmology - Seth K. Asante, Bianca Dittrich, José Padua-Argüelles

  2. [2112.15418] - Tests For Maximum Force and Maximum Power - Christoph Schiller

  3. [2112.14848] - Holographic CFT Phase Transitions and Criticality for Charged AdS Black Holes - Wan Cong, David Kubiznak, Robert Mann, Manus Visser

  4. [2112.15086] - Palatini Higgs inflation and the refined dS conjecture - Yang Liu

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