Sun - 11/20/22

There is no new related paper today

Spin foams, Refinement limit and Renormalization

  • Authors: Seth K. Asante, Bianca Dittrich, Sebastian Steinhaus
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2211.09578
  • Abstract Spin foams provide path integrals for quantum gravity, which employ discretizations as regulator. To obtain regulator independent predictions, we must remove these fiducial structures in a suitable refinement limit. In this chapter we present the current state of research: We begin with a discussion on the role of diffeomorphism symmetries in discrete systems, the notion of scale in background independent theories and how we can consistently improve theories via renormalization to reduce regulator dependence. We present the consistent boundary formulation, which provides a renormalization framework for background independent theories, and discuss tensor network methods and restricted spin foams, which provide concrete renormalization algorithms aiming at the construction of consistent boundary amplitudes for spin foams. We furthermore discuss effective spin foams, which have allowed for the construction of a perturbative refinement limit and an associated effective continuum action.

  1. [2211.09192] - Stability properties of Regular Black Holes - Alfio Bonanno, Frank Saueressig

  2. [2211.09128] - Holographic origin of TCC and the Distance Conjecture - Alek Bedroya

Sat - 11/19/22

There is no new related paper today

Spin foams, Refinement limit and Renormalization

  • Authors: Seth K. Asante, Bianca Dittrich, Sebastian Steinhaus
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2211.09578
  • Abstract Spin foams provide path integrals for quantum gravity, which employ discretizations as regulator. To obtain regulator independent predictions, we must remove these fiducial structures in a suitable refinement limit. In this chapter we present the current state of research: We begin with a discussion on the role of diffeomorphism symmetries in discrete systems, the notion of scale in background independent theories and how we can consistently improve theories via renormalization to reduce regulator dependence. We present the consistent boundary formulation, which provides a renormalization framework for background independent theories, and discuss tensor network methods and restricted spin foams, which provide concrete renormalization algorithms aiming at the construction of consistent boundary amplitudes for spin foams. We furthermore discuss effective spin foams, which have allowed for the construction of a perturbative refinement limit and an associated effective continuum action.

  1. [2211.09192] - Stability properties of Regular Black Holes - Alfio Bonanno, Frank Saueressig

  2. [2211.09128] - Holographic origin of TCC and the Distance Conjecture - Alek Bedroya

Fri - 11/18/22

There is no new related paper today

Spin foams, Refinement limit and Renormalization

  • Authors: Seth K. Asante, Bianca Dittrich, Sebastian Steinhaus
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2211.09578
  • Abstract Spin foams provide path integrals for quantum gravity, which employ discretizations as regulator. To obtain regulator independent predictions, we must remove these fiducial structures in a suitable refinement limit. In this chapter we present the current state of research: We begin with a discussion on the role of diffeomorphism symmetries in discrete systems, the notion of scale in background independent theories and how we can consistently improve theories via renormalization to reduce regulator dependence. We present the consistent boundary formulation, which provides a renormalization framework for background independent theories, and discuss tensor network methods and restricted spin foams, which provide concrete renormalization algorithms aiming at the construction of consistent boundary amplitudes for spin foams. We furthermore discuss effective spin foams, which have allowed for the construction of a perturbative refinement limit and an associated effective continuum action.

  1. [2211.09192] - Stability properties of Regular Black Holes - Alfio Bonanno, Frank Saueressig

  2. [2211.09128] - Holographic origin of TCC and the Distance Conjecture - Alek Bedroya

Thu - 11/17/22

There is no new related paper today

There is no new related paper today

  1. [2211.08793] - Non-thermal acceleration radiation of atoms near a black hole in presence of dark energy - Syed Masood A. S. Bukhari, Imtiyaz Ahmad Bhat, Chenni Xu, Li-Gang Wang

  2. [2211.08839] - DHOST gravity in Ultra-diffuse galaxies – Part II: NGC 1052-DF4 and Dragonfly 44 - Enrico Laudato, Vincenzo Salzano

Wed - 11/16/22

There is no new related paper today

There is no new related paper today

Tue - 11/15/22

Investigating Loop Quantum Gravity with EHT Observational Effects of Rotating Black holes

  • Authors: Shafqat Ul Islam, Jitendra Kumar, Rahul Kumar Walia, Sushant G. Ghosh
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2211.06653
  • Abstract A mathematically consistent rotating black hole model in Loop Quantum Gravity (LQG) is yet lacking. The scarcity of rotating black hole solutions in LQG substantially hampers the development of testing LQG from observations, e.g., from the Event Horizon Telescope (EHT) observations. The EHT observation revealed event horizon-scale images of the supermassive black holes Sgr A* and M87. The EHT results are consistent with the shadow of a Kerr black hole of general relativity. We present LQG-motivated rotating black hole spacetimes (LMRBH), which are regular everywhere and asymptotically encompass the Kerr black hole as a particular case. LMRBH metric describes a multi-horizon black hole in the sense that it can admit up to three horizons, such that an extremal LMRBH, unlike Kerr black hole, refers to a black hole with angular momentum $a>M$. The metric, depending on the parameters, describes (1) black holes with only one horizon (BH-I), (2) black holes with an event and Cauchy horizons (BH-II), (3) black holes with three horizons (BH-III) or (4) no-horizon spacetime (NH) which, we show, is almost ruled out by the EHT observations. We constrain the LQG parameter with an aid of the EHT shadow observational results of M87 and Sgr A,respectively, for an inclination angle of $17^0$ and $50^0$. In particular, the VLTI bound for the Sgr A, $\delta\in (-0.17,0.01)$, constrains the parameters ($a,l$) such that for $0< l\leq 0.347851M\; (l\leq 2\times 10^6$ Km), the allowed range of $a$ is $(0,1.0307M)$. Together with EHT bounds of Sgr A$^$ and M87$^$ observables, our analysis concludes that the substantial part of BH-I and BH-II parameter space agrees with the EHT results of M87* and Sgr A. While EHT M87 results totally rules out the BH-III, but not that by Sgr A*.

Philosophical Foundations of Loop Quantum Gravity

  • Authors: Carlo Rovelli, Francesca Vidotto
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2211.06718
  • Abstract Understanding the quantum aspects of gravity is not only a matter of equations and experiments. Gravity is intimately connected with the structure of space and time, and understanding quantum gravity requires us to find a conceptual structure appropriate to make sense of the quantum aspects of space and time. In the course of the last decades, an extensive discussion on this problem has led to a clear conceptual picture, that provides a coherent conceptual foundation of today’s Loop Quantum Gravity. We review this foundation, addressing issues such as the sense in which space and time are emergent, the notion of locality, the role of truncation that enables physical computations on finite graphs, the problem of time, and the characterization of the observable quantities in quantum gravity.

The weak coupling theory of all dimensional loop quantum gravity

  • Authors: Gaoping Long, Chun-Yen Lin
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph)
  • Arxiv link: https://arxiv.org/abs/2211.07498
  • Abstract The weak coupling loop quantum theory with Abelian gauge group provides us a new perspective to study the weak coupling properties of LQG. In this paper, the weak coupling theory of all dimensional loop quantum gravity is established based on a symplectic-morphism between the $SO(D+1)$ holonomy-flux phase space and the $U(1)^{\frac{D(D+1)}{2}}$ holonomy-flux phase space. More explicitly, the Gaussian, simplicity, diffeomorphism and scalar constraint operators in $SO(D+1)$ loop quantum gravity will be generalized to the $U(1)^{\frac{D(D+1)}{2}}$ loop quantum theory based on the symplectic-morphism, and the $U(1)^{\frac{D(D+1)}{2}}$ loop quantum theory equipped with these constraint operators gives the weak coupling $U(1)^{\frac{D(D+1)}{2}}$ loop quantum gravity, with the corresponding Hilbert space is composed by the $U(1)^{\frac{D(D+1)}{2}}$ heat-kernel coherent states which are peaked at the weak coupling region of the $U(1)^{\frac{D(D+1)}{2}}$ holonomy-flux phase space.

On topology changes in quantum field theory and quantum gravity

  • Authors: Benjamin Schulz
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph)
  • Arxiv link: https://arxiv.org/abs/2211.07017
  • Abstract Two singularity theorems can be proven if one attempts to let a Lorentzian cobordism interpolate between two topologically distinct manifolds. On the other hand, Cartier and DeWitt-Morette have given a rigorous definition for quantum field theories (qfts) by means of path integrals. This article uses their results to study whether qfts can be made compatible with topology changes. We show that path integrals over metrics need a finite norm for the latter and for degenerate metrics, this problem can sometimes be resolved with tetrads. We prove that already in the neighborhood of some cuspidal singularities, difficulties can arise to define certain qfts. On the other hand, we show that simple qfts can be defined around conical singularities that result from a topology change in a simple setup. We argue that the ground state of many theories of quantum gravity will imply a small cosmological constant and, during the expansion of the universe, frequent topology changes. Unfortunately, it is difficult to describe the transition amplitudes consistently due to the aforementioned problems. We argue that one needs to describe qfts by stochastic differential equations, and in the case of gravity, by Regge calculus in order to resolve this problem.
  1. [2211.07633] - Constraints on Sequential Discontinuities from the Geometry of On-shell Spaces - Holmfridur S. Hannesdottir, Andrew J. McLeod, Matthew D. Schwartz, Cristian Vergu

Mon - 11/14/22

There is no new related paper today

Integrability and BRST invariance from BF topological theory

  • Authors: A. Restuccia, A. Sotomayor
  • Subjects: Mathematical Physics (math-ph)
  • Arxiv link: https://arxiv.org/abs/2211.05914
  • Abstract We consider the BRST invariant effective action of the non-abelian BF topological theory in $1+1$ dimensions with gauge group $Sl(2,\mathbb{R})$. By considering different gauge fixing conditions, the zero-curvature field equation give rise to several well known integrable equations. We prove that each integrable equation together with the associated ghost field evolution equation, obtained from the BF theory, is a BRST invariant system with an infinite sequence of BRST invariant conserved quantities. We construct explicitly the systems and the BRST transformation laws for the KdV sequence (including the KdV, mKdV and CKdV equations) and Harry Dym integrable equation.

  1. [2211.05817] - A connection between regular black holes and horizonless ultracompact stars - Raúl Carballo-Rubio, Francesco Di Filippo, Stefano Liberati, Matt Visser

  2. [2211.05806] - Holography for bulk states in 3D quantum gravity - Joris Raeymaekers, Gideon Vos

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