Fri - 12/10/21

There is no new related paper today

There is no new related paper today

  1. [2112.04609] - Minimal Length Phenomenology and the Black Body Radiation - Pasquale Bosso, Juan Manuel López Vega

  2. [2112.04647] - Astrophysically viable Kerr-like spacetime – into the eye of the storm - Alex Simpson, Matt Visser

Thu - 12/09/21

On propagation in Loop Quantum Gravity

  • Authors: Thomas Thiemann, Madhavan Varadarajan
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Lattice (hep-lat); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph)
  • Arxiv link: https://arxiv.org/abs/2112.03992
  • Abstract A rigorous implementation of the Wheeler-Dewitt equations was derived in the context of Loop Quantum Gravity (LQG) and was coined Quantum Spin Dynamics (QSD). The Hamiltonian constraint of QSD was criticised as being too local and to prevent “propagation” in canonical LQG. That criticism was based on an algorithm developed for QSD for generating solutions to the Wheeler-DeWitt equations. The fine details of that algorithm could not be worked out because the QSD Hamiltonian constraint makes crucial use of the volume operator which cannot be diagonalised analytically. In this paper, we consider the U(1)$^3$ model for Euclidean vacuum LQG which consists in replacing the structure group SU(2) by U(1)$^3$ and otherwise keeps all properties of the SU(2) theory intact. This enables analytical calculations and the fine details of the algorithm {\it can} be worked out. By considering one of the simplest possible non-trivial class of solutions based on very small graphs, we show that 1. an infinite number of solutions {\it exist} which are 2. generically {\it not normalisable} with respect to the inner product on the space of spatially diffeomorphism invariant distributions and 3. generically display {\it propagation}. Due to the closeness of the U(1)$^3$ model to Euclidean LQG, it is extremely likely that all three properties hold also in the SU(2) case and even more so in physical Lorentzian LQG. These arguments can in principle be made water tight using modern numerical (e.g. ML or QC) methods combined with the techniques developed in this paper which we reserve for future work.

There is no new related paper today

  1. [2112.03954] - Black Holes in Klein Space - Erin Crawley, Alfredo Guevara, Noah Miller, Andrew Strominger

Wed - 12/08/21

Perfect discretizations as a gateway to one-loop partition functions for 4D gravity

  • Authors: Seth K. Asante, Bianca Dittrich
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2112.03307
  • Abstract Lattice actions and amplitudes that perfectly mirror continuum physics are known as perfect discretizations. Such perfect discretizations naturally preserve the symmetries of the continuum. This is a key concern for general relativity, where diffeomorphism symmetry and dynamics are deeply connected, and diffeomorphisms play a crucial role in quantization. In this work we construct for the first time a perfect discretizations for four-dimensional linearized gravity. We show how the perfect discretizations do lead to a straightforward construction of the one-loop quantum corrections for manifolds with boundary. This will also illustrate, that for manifolds with boundaries, gauge modes that affect the boundary, need to be taken into account for the computation of the one-loop correction. This work provides therefore an evaluation of the boundary action for the diffeomorphism modes for a general class of backgrounds.

There is no new related paper today

  1. [2112.03778] - Emergent time, cosmological constant and boundary dimension at infinity in combinatorial quantum gravity - Carlo A. Trugenberger

  2. [2112.03793] - One-dimensional Quantum Gravity and the Schwarzian theory - Dionysios Anninos, Diego M. Hofman, Stathis Vitouladitis

Tue - 12/07/21

Quantum speed limit and stability of coherent states in quantum gravity

  • Authors: Klaus Liegener, Łukasz Rudnicki
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Lattice (hep-lat); Quantum Physics (quant-ph)
  • Arxiv link: https://arxiv.org/abs/2112.01597
  • Abstract Utilizing the program of expectation values in coherent states and its recently developed algorithmic tools, this letter investigates the dynamical properties of cosmological coherent states for Loop Quantum Gravity. To this end, the Quantum Speed Limit is adapted to Quantum Gravity, yielding necessary consistency checks for any proposal of stable families of states. To showcase the strength of the developed tools, they are applied to a prominent model: the Euclidean part of the quantum scalar constraint. We report the variance of this constraint evaluated on a family of coherent states showing that, for short times, this family passes the Quantum Speed Limit test, allowing the transition from one coherent state to another one.

There is no new related paper today

  1. [2112.01974] - On Quadratic Gravity - John F. Donoghue, Gabriel Menezes

Mon - 12/06/21

Quantum speed limit and stability of coherent states in quantum gravity

  • Authors: Klaus Liegener, Łukasz Rudnicki
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Lattice (hep-lat); Quantum Physics (quant-ph)
  • Arxiv link: https://arxiv.org/abs/2112.01597
  • Abstract Utilizing the program of expectation values in coherent states and its recently developed algorithmic tools, this letter investigates the dynamical properties of cosmological coherent states for Loop Quantum Gravity. To this end, the Quantum Speed Limit is adapted to Quantum Gravity, yielding necessary consistency checks for any proposal of stable families of states. To showcase the strength of the developed tools, they are applied to a prominent model: the Euclidean part of the quantum scalar constraint. We report the variance of this constraint evaluated on a family of coherent states showing that, for short times, this family passes the Quantum Speed Limit test, allowing the transition from one coherent state to another one.

There is no new related paper today

  1. [2112.01974] - On Quadratic Gravity - John F. Donoghue, Gabriel Menezes

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