Fri - 03/31/23

Stationary cosmology in group field theory

  • Authors: Steffen Gielen, Robert Santacruz
  • Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2303.16942
  • Abstract Group field theory (GFT) models for quantum gravity coupled to a massless scalar field give rise to cosmological models that reproduce the (expanding or contracting) dynamics of homogeneous and isotropic spacetimes in general relativity at low energies, while including high-energy corrections that lead to singularity resolution by a “bounce.” Here we investigate two possibilities for obtaining stationary solutions in GFT cosmology, which could be useful as an analogue of Minkowski spacetime. We first focus on a limit in which interactions are neglected and the effective Newton’s constant in GFT cosmology is taken to zero. In this limit, we derive an effective Friedmann equation that shows no stationary solutions, but departures from the trivial classical dynamics falling off rapidly, similar to the usual correction terms responsible for the bounce. Since the effective Newton’s constant needs to be exactly zero, the scenario is fine-tuned. A more satisfactory approach is obtained in a weakly interacting model: we find bound states with sharply peaked volume, representing a stationary semiclassical cosmology, and show that coherent states peaked around the minimum of the potential remain stable with small quantum fluctuations, and only small oscillations around a nearly constant volume. These coherent states realise the idea of a “quantum gravity condensate.”

There is no new related paper today

  1. [2303.16924] - Regular Black Holes and Stars from Analytic $f(F^2)$ - Zhi-Chao Li, H. Lu

  2. [2303.17238] - Non-commutative coordinates from quantum gravity - Markus B. Fröb, Albert Much, Kyriakos Papadopoulos

  3. [2303.17552] - Structure Formation in Non-local Bouncing Models - D. Jackson, R. Bufalo

Thu - 03/30/23

Numerics of Bianchi type II and type IX spacetimes in effective loop quantum cosmology

  • Authors: Timothy Blackmore, Edward Wilson-Ewing
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2303.16747
  • Abstract We numerically solve the effective loop quantum cosmology dynamics for the vacuum Bianchi type II and type IX spacetimes, in particular studying how the Kasner exponents evolve across the loop quantum cosmology bounce. We find that when the spatial curvature is negligible at the bounce then the Kasner exponents transform according to the same simple equation as for a Bianchi type I spacetime in effective loop quantum cosmology, while there are departures from this transformation rule in cases where the spatial curvature is significant during the bounce. We also use high-precision numerics to compute the evolution of a Bianchi type IX spacetime through multiple bounces and recollapses, and find indications of chaotic behaviour. Interestingly, the numerics indicate that it is during the classical recollapse, and not the loop quantum cosmology bounce, that nearby solutions diverge most strongly.

There is no new related paper today

  1. [2303.16315] - The Hilbert space of de Sitter quantum gravity - Tuneer Chakraborty, Joydeep Chakravarty, Victor Godet, Priyadarshi Paul, Suvrat Raju

  2. [2303.16316] - Holography of information in de Sitter space - Tuneer Chakraborty, Joydeep Chakravarty, Victor Godet, Priyadarshi Paul, Suvrat Raju

  3. [2303.16380] - The Timelike Tube Theorem in Curved Spacetime - Alexander Strohmaier, Edward Witten

  4. [2303.16838] - Reanalysis of critical exponents for the O(N) model via a hydrodynamic approach to the Functional Renormalization Group - Fabrizio Murgana, Adrian Koenigstein, Dirk H. Rischke

Wed - 03/29/23

The topological order in loop quantum gravity

  • Authors: Jingbo Wang
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2303.15760
  • Abstract Topological order (long-range entanglement) is a new type of order that beyond Landau’s symmetry breaking theory. This concept plays important roles in modern condensed matter physics. The topological entanglement entropy provides a universal quantum number to characterize the topological order in a system. The topological entanglement entropy of the BTZ black hole was calculated and found that it coincides with that for fractional quantum Hall states. So the BTZ black hole has the same topological order with the fractional quantum Hall state. We show that the four dimensional black hole can also have topological order, by showing that the topological entanglement entropy of black holes is non-zero in loop quantum gravity. We also consider the Hamiltonian constraint in loop quantum gravity. By comparing with the BF theory, we found that the physical Hilbert space for loop quantum gravity is degenerate on non-trivial manifold, which indicate the existence of topological order in loop quantum gravity. We advise to bring in the methods and results in string-net condensation to loop quantum gravity to solve some difficult problems.

The topological order in loop quantum gravity

  • Authors: Jingbo Wang
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2303.15760
  • Abstract Topological order (long-range entanglement) is a new type of order that beyond Landau’s symmetry breaking theory. This concept plays important roles in modern condensed matter physics. The topological entanglement entropy provides a universal quantum number to characterize the topological order in a system. The topological entanglement entropy of the BTZ black hole was calculated and found that it coincides with that for fractional quantum Hall states. So the BTZ black hole has the same topological order with the fractional quantum Hall state. We show that the four dimensional black hole can also have topological order, by showing that the topological entanglement entropy of black holes is non-zero in loop quantum gravity. We also consider the Hamiltonian constraint in loop quantum gravity. By comparing with the BF theory, we found that the physical Hilbert space for loop quantum gravity is degenerate on non-trivial manifold, which indicate the existence of topological order in loop quantum gravity. We advise to bring in the methods and results in string-net condensation to loop quantum gravity to solve some difficult problems.

  1. [2303.15546] - The path integral formulation of energetic causal set models of the universe - Lee Smolin

  2. [2303.15645] - Triple Interference, Non-linear Talbot Effect and Gravitization of the Quantum - Per Berglund, Andrew Geraci, Tristan Hübsch, David Mattingly, Djordje Minic

  3. [2303.15903] - Small Black Hole Explosions - Roberta Angius, Jesus Huertas, Angel M. Uranga

  4. [2303.15921] - Pole-skipping of gravitational waves in the backgrounds of four-dimensional massive black holes - Sašo Grozdanov, Mile Vrbica

Tue - 03/28/23

There is no new related paper today

There is no new related paper today

  1. [2303.14854] - No Time for Time from No-Time - Eugene Y. S. Chua, Craig Callender

  2. [2303.14945] - Quantum matter core of black holes (and quantum hair) - Roberto Casadio, Octavian Micu

Mon - 03/27/23

There is no new related paper today

There is no new related paper today

  1. [2303.13580] - Bounds on Species Scale and the Distance Conjecture - Damian van de Heisteeg, Cumrun Vafa, Max Wiesner

  2. [2303.13884] - One-loop algebras and fixed flow trajectories in adjoint multi-scalar gauge theory - Nadia Flodgren, Bo Sundborg

  3. [2303.14160] - On Perturbative Quantum Gravity with a Cosmological Constant - David Prinz

New papers last week