Fri - 11/17/23

There is no new related paper today

There is no new related paper today

  1. [2311.09284] - All Loop Scattering For All Multiplicity - Nima Arkani-Hamed, Hadleigh Frost, Giulio Salvatori, Pierre-Guy Plamondon, Hugh Thomas

  2. [2311.09978] - Gauging spacetime inversions in quantum gravity - Daniel Harlow, Tokiro Numasawa

Thu - 11/16/23

On the classicality and uniqueness in loop quantization of Bianchi-I spacetimes

  • Authors: Meysam Motaharfar, Parampreet Singh, Eklavya Thareja
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2311.08465
  • Abstract In loop quantum cosmology, ambiguities in the Hamiltonian constraint can result in models with varying phenomenological predictions. In the homogeneous isotropic models, these ambiguities were settled, and the improved dynamics was found to be a unique and phenomenologically viable choice. This issue has remained unsettled on the inclusion of anisotropies, and in the Bianchi-I model there exist two generalizations of isotropic improved dynamics. In the first of these, labelled as $\bar \mu$ quantization, the edge length of holonomies depends on the inverse of the directional scale factor. This quantization has been favored since it results in universal bounds on energy density and anisotropic shear, and can be viably formulated for non-compact as well as compact spatial manifolds. However, there exists an earlier quantization, labelled as $\bar \mu’$ quantization, where edge lengths of holonomies depend on the inverse of the square root of directional triads. This quantization is also non-singular and so far believed to yield a consistent physical picture for spatially compact manifolds. We examine the issue of the physical viability of these quantizations for different types of matter in detail by performing a large number of numerical simulations. Our analysis reveals certain limitations which have so far remained unnoticed. We find that while being non-singular, the $\bar \mu’$ quantization suffers from a surprising problem where one of the triad components and associated polymerized term retains Planckian character even at large volumes. As a result, not only is the anisotropic shear not preserved across the bounce, which is most highlighted in the vacuum case, but the universe can exhibit an unexpected cyclic evolution. These problematic features are absent from the $\bar \mu$ quantization leaving it as the only viable prescription for loop quantizing the Bianchi-I model.

Quantum Group Intertwiner Space From Quantum Curved Tetrahedron

  • Authors: Muxin Han, Chen-Hung Hsiao, Qiaoyin Pan
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph)
  • Arxiv link: https://arxiv.org/abs/2311.08587
  • Abstract In this paper, we develop a quantum theory of homogeneously curved tetrahedron geometry, by applying the combinatorial quantization to the phase space of tetrahedron shapes defined in arXiv:1506.03053. Our method is based on the relation between this phase space and the moduli space of SU(2) flat connections on a 4-punctured sphere. The quantization results in the physical Hilbert space as the solution of the quantum closure constraint, which quantizes the classical closure condition $M_4M_3M_2M_1=1$, $M_\nu\in$ SU(2), for the homogeneously curved tetrahedron. The quantum group Uq(su(2)) emerges as the gauge symmetry of a quantum tetrahedron. The physical Hilbert space of the quantum tetrahedron coincides with the Hilbert space of 4-valent intertwiners of Uq(su(2)). In addition, we define the area operators quantizing the face areas of the tetrahedron and compute the spectrum. The resulting spectrum is consistent with the usual Loop-Quantum-Gravity area spectrum in the large spin regime but is different for small spins. This work closely relates to 3+1 dimensional Loop Quantum Gravity in presence of cosmological constant and provides a justification for the emergence of quantum group in the theory.

Finite temperature quantum field theory under the influence of 3D lattices

  • Authors: Lucia Santamaria-Sanz
  • Subjects: Mathematical Physics (math-ph)
  • Arxiv link: https://arxiv.org/abs/2311.08435
  • Abstract The one-loop quantum corrections to the internal energy of lattices due to the quantum fluctuations of the scalar field of phonons are studied. The band spectrum of the lattice is characterised in terms of the scattering data, allowing to compute the total Helmholtz free energy and the entropy at finite non zero temperature. Some examples of three dimensional periodic potentials built from the repetition of the same punctual or compact supported potential are addressed: the generalised Dirac comb and the P"oschl-Teller comb, respectively.

There is no new related paper today

  1. [2311.08616] - Emergent modified gravity: The perfect fluid and gravitational collapse - Erick I. Duque

  2. [2311.09171] - Harada-Maxwell Static Spherically Symmetric Spacetimes - Alan Barnes

Wed - 11/15/23

There is no new related paper today

There is no new related paper today

  1. [2311.07979] - On the moduli space curvature at infinity - Fernando Marchesano, Luca Melotti, Lorenzo Paoloni

Tue - 11/14/23

On the initial state of the universe in Loop Quantum Cosmology and the time arrow

  • Authors: Carlos Silva, Renan Aragão, Francisco A. Brito
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2311.05670
  • Abstract In this work, we address the thermodynamical evolution of the universe in the context of Loop Quantum Cosmology by considering the conditions for the existence of a time arrow in this approach. We find out that, for the existence of a time arrow in our universe, in terms of its obedience to the Generalized Second Law of Thermodynamics, the initial state of the cosmos must correspond to a negative entropy one.

Quantization of spherically symmetric loop quantum gravity coupled to a scalar field and a clock: the asymptotic limit

  • Authors: Rodolfo Gambini, Jorge Pullin
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2311.05766
  • Abstract We continue our work on the study of spherically symmetric loop quantum gravity coupled to two spherically symmetric scalar fields, one which acts as a clock. As a consequence of the presence of the latter, we can define a true Hamiltonian for the theory. The spherically symmetric context allows to carry out precise detailed calculations. Here we study the theory for regions of large values of the radial coordinate. This allows us to define in detail the vacuum of the theory and study its quantum states, yielding a quantum field theory on a quantum space time that makes contact with the usual treatment on classical space times.

There is no new related paper today

Mon - 11/13/23

On the initial state of the universe in Loop Quantum Cosmology and the time arrow

  • Authors: Carlos Silva, Renan Aragão, Francisco A. Brito
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2311.05670
  • Abstract In this work, we address the thermodynamical evolution of the universe in the context of Loop Quantum Cosmology by considering the conditions for the existence of a time arrow in this approach. We find out that, for the existence of a time arrow in our universe, in terms of its obedience to the Generalized Second Law of Thermodynamics, the initial state of the cosmos must correspond to a negative entropy one.

Quantization of spherically symmetric loop quantum gravity coupled to a scalar field and a clock: the asymptotic limit

  • Authors: Rodolfo Gambini, Jorge Pullin
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2311.05766
  • Abstract We continue our work on the study of spherically symmetric loop quantum gravity coupled to two spherically symmetric scalar fields, one which acts as a clock. As a consequence of the presence of the latter, we can define a true Hamiltonian for the theory. The spherically symmetric context allows to carry out precise detailed calculations. Here we study the theory for regions of large values of the radial coordinate. This allows us to define in detail the vacuum of the theory and study its quantum states, yielding a quantum field theory on a quantum space time that makes contact with the usual treatment on classical space times.

There is no new related paper today

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