Fri - 02/10/23

A diffeomorphism invariant family of metric-affine actions for loop cosmologies

  • Authors: Adrià Delhom, Gonzalo J. Olmo, Parampreet Singh
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2302.04285
  • Abstract In loop quantum cosmology (LQC) the big bang singularity is generically resolved by a big bounce. This feature holds even when modified quantization prescriptions of the Hamiltonian constraint are used such as in mLQC-I and mLQC-II. While the latter describes a symmetric bounce as in standard LQC, the former describes an asymmetric bounce with an emergent Planckian de-Sitter pre-bounce phase. We consider the potential relation of these canonically quantized non-singular models with effective actions based on a geometric description. We find a 3-parameter family of metric-affine $f(\mathcal{R})$ theories which accurately approximate the effective dynamics of LQC and mLQC-II in all regimes and mLQC-I in the post-bounce phase. Two of the parameters are fixed by enforcing equivalence at the bounce, and the background evolution of the relevant observables can be fitted with only one free parameter. It is seen that the non-perturbative effects of these loop cosmologies are universally encoded by a logarithmic correction that only depends on the bounce curvature of the model. In addition, we find that the best fit value of the free parameter can be very approximately written in terms of fundamental parameters of the underlying quantum description for the three models. The values of the best fits can be written in terms of the bounce density in a simple manner, and the values for each model are related to one another by a proportionality relation involving only the Barbero-Immirzi parameter.

There is no new related paper today

  1. [2302.04272] - Black Holes in Asymptotically Safe Gravity - Alessia Platania

  2. [2302.04766] - Interference and reflection from the event horizon of a quantum corrected black hole - Sunandan Gangopadhyay, Soham Sen, Rituparna Mandal

  3. [2302.04275] - The Tameness of Quantum Field Theory, Part II – Structures and CFTs - Michael R. Douglas, Thomas W. Grimm, Lorenz Schlechter

  4. [2302.04564] - The minimal length: a cut-off in disguise? - Pasquale Bosso, Luciano Petruzziello, Fabian Wagner

  5. [2302.04697] - Schur-like index of the Klebanov-Witten theory via the AdS/CFT correspondence - Shota Fujiwara

  6. [2302.04736] - Numerical RG-time integration of the effective potential: Analysis and Benchmark - Friederike Ihssen, Franz R. Sattler, Nicolas Wink

Thu - 02/09/23

There is no new related paper today

There is no new related paper today

  1. [2302.03692] - Holographic Einstein rings of a Gauss-Bonnet AdS black hole - Xiao-Xiong Zeng, Ke-Jian He, Guo-ping Li

  2. [2302.03710] - Bouncing cosmology from nonlinear dark energy with two cosmological constants - Molly Burkmar, Marco Bruni

  3. [2302.03847] - Gauge theories with non-trivial boundary conditions II: Black holes - Peng Cheng

Wed - 02/08/23

A Fock space structure for the diffeomorphism invariant Hilbert space of loop quantum gravity and its applications

  • Authors: Hanno Sahlmann, Waleed Sherif
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph)
  • Arxiv link: https://arxiv.org/abs/2302.03612
  • Abstract Loop quantum gravity (LQG) is a quantization program for gravity based on the principles of QFT and general covariance of general relativity. Quantum states of LQG describe gravitational excitations based on graphs embedded in a spatial slice of spacetime. We show that, under certain assumptions on the class of diffeomorphisms, the space of diffeomorphism invariant states carries a Fock space structure. The role of one-particle excitations for this structure is played by the diffeomorphism invariant states based on graphs with a single (linked) component. This means, however, that a lot of the structure of the diffeomorphism invariant Hilbert space remains unresolved by this structure. We show how the Fock structure allows to write at least some condensate states of group field theory as diffeomorphism invariant coherent states of LQG in a precise sense. We also show how to construct other interesting states using this Fock structure. We finally explore the quantum geometry of single- and multi-particle states and tentatively observe some resemblance to geometries with a single or multiple components, respectively.

Loop Quantum Cosmology of non-diagonal Bianchi models

  • Authors: Matteo Bruno, Giovanni Montani
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2302.03638
  • Abstract The non-diagonal Bianchi models are studied in the loop framework for their classical and quantum formulation. The expressions of the Ashtekar-Barbero-Immirzi variables and their properties are found to provide a loop quantization of these models. In the special case of Bianchi I Universe, it is shown that the geometrical operators result invariant from the diagonal description. Hence, the kinematical Hilbert space of the non-diagonal Bianchi I model has similar features to the diagonal one.

There is no new related paper today

  1. [2302.03259] - Relativity and decoherence of spacetime superpositions - Joshua Foo, Robert B. Mann, Magdalena Zych

  2. [2302.03688] - A 10d construction of Euclidean axion wormholes in flat and AdS space - Gregory J. Loges, Gary Shiu, Thomas Van Riet

Tue - 02/07/23

Emergence of Riemannian Quantum Geometry

  • Authors: Hal M. Haggard, Jerzy Lewandowski, Hanno Sahlmann
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph)
  • Arxiv link: https://arxiv.org/abs/2302.02840
  • Abstract In this chapter we take up the quantum Riemannian geometry of a spatial slice of spacetime. While researchers are still facing the challenge of observing quantum gravity, there is a geometrical core to loop quantum gravity that does much to define the approach. This core is the quantum character of its geometrical observables: space and spacetime are built up out of Planck-scale quantum grains. The interrelations between these grains are described by spin networks, graphs whose edges capture the bounding areas of the interconnected nodes, which encode the extent of each grain. We explain how quantum Riemannian geometry emerges from two different approaches: in the first half of the chapter we take the perspective of continuum geometry and explain how quantum geometry emerges from a few principles, such as the general rules of canonical quantization of field theories, a classical formulation of general relativity in which it appears embedded in the phase space of Yang-Mills theory, and general covariance. In the second half of the chapter we show that quantum geometry also emerges from the direct quantization of the finite number of degrees of freedom of the gravitational field encoded in discrete geometries. These two approaches are complimentary and are offered to assist readers with different backgrounds enter the compelling arena of quantum Riemannian geometry.

There is no new related paper today

  1. [2302.01992] - Newtonion Quantum Gravity, WIMPs and Celestial Mechanics – Summary of Results - Richard Durran, Andrew Neate, Aubrey Truman

  2. [2302.02133] - Nonsingular black hole chemistry in $4D$ Einstein-Gauss-Bonnet gravity - Arun Kumar, Sushant G. Ghosh

  3. [2302.02784] - Accretion disk around regular black holes - Amin Rezaei Akbarieh, Minou Khoshragbaf, Mohammad Atazadeh

  4. [2302.02800] - Black hole image encoding quantum gravity information - Cong Zhang, Yongge Ma, Jinsong Yang

  5. [2302.01958] - Notes on the type classification of von Neumann algebras - Jonathan Sorce

  6. [2302.02446] - Toward random tensor networks and holographic codes in CFT - Jeevan Chandra, Thomas Hartman

  7. [2302.02961] - Double excitations in the AdS(5)/CFT(4) integrable system and the Lagrange operator - Burkhard Eden, Dennis le Plat, Anne Spiering

  8. [2302.02709] - Analytic states in quantum field theory on curved spacetimes - Alexander Strohmaier, Edward Witten

Mon - 02/06/23

There is no new related paper today

There is no new related paper today

  1. [2302.01580] - Rotating BTZ-like black hole and central charges in Einstein-bumblebee gravity - Chikun Ding, Yu Shi, Jun Chen, Yuebing Zhou, Changqing Liu, Yuehua Xiao

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