Fri - 03/15/24

Spinfoam Models for Quantum Gravity: Overview

  • Authors: Etera R. Livine
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2403.09364
  • Abstract In the quest of a physical theory of quantum gravity, spin foam models, or in short spinfoams, propose a well-defined path integral summing over quantized discrete space-time geometries. At the crossroad of topological quantum field theory, dynamical triangulations, Regge calculus, and loop quantum gravity, this framework provides a non-perturbative and background independent quantization of general relativity. It defines transition amplitudes between quantum states of geometry, and gives a precise picture of the Planck scale geometry with quantized areas and volumes. Gravity in three space-time dimensions is exactly quantized in terms of the Ponzano-Regge state-sum and Turaev-Viro topological invariants. In four space-time dimensions, gravity is formulated as a topological theory, of the BF type, with extra constraints, and hence quantized as a topological state-sum filled with defects. This leads to the Engle-Pereira-Rovelli-Livine (EPRL) spinfoam model, that can be used for explicit quantum gravity computations, for example for resolving the Big Bang singularity by a bounce or in black-to-white hole transition probability amplitudes.

Spinfoam Models for Quantum Gravity: Overview

  • Authors: Etera R. Livine
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2403.09364
  • Abstract In the quest of a physical theory of quantum gravity, spin foam models, or in short spinfoams, propose a well-defined path integral summing over quantized discrete space-time geometries. At the crossroad of topological quantum field theory, dynamical triangulations, Regge calculus, and loop quantum gravity, this framework provides a non-perturbative and background independent quantization of general relativity. It defines transition amplitudes between quantum states of geometry, and gives a precise picture of the Planck scale geometry with quantized areas and volumes. Gravity in three space-time dimensions is exactly quantized in terms of the Ponzano-Regge state-sum and Turaev-Viro topological invariants. In four space-time dimensions, gravity is formulated as a topological theory, of the BF type, with extra constraints, and hence quantized as a topological state-sum filled with defects. This leads to the Engle-Pereira-Rovelli-Livine (EPRL) spinfoam model, that can be used for explicit quantum gravity computations, for example for resolving the Big Bang singularity by a bounce or in black-to-white hole transition probability amplitudes.
  1. [2403.08991] - Barrow Entropy and AdS Black Holes in RPS Thermodynamics - Yahya Ladghami, Brahim Asfour, Amine Bouali, Ahmed Errahmani, Taoufik Ouali

Thu - 03/14/24

One-Loop Quantum Stress-Energy Tensor for the Kink and sine-Gordon Solitons

  • Authors: Noah Graham, Herbert Weigel
  • Subjects: High Energy Physics - Theory (hep-th); High Energy Physics - Phenomenology (hep-ph)
  • Arxiv link: https://arxiv.org/abs/2403.08677
  • Abstract We compute the renormalized one-loop quantum corrections to the energy density $T_{00}(x)$ and pressure $T_{11}(x)$ for solitons in the $1+1$ dimensional scalar sine-Gordon and kink models. We show how precise implementation of counterterms in dimensional regularization resolves previously identified discrepancies between the integral of $T_{00}(x)$ and the known correction to the total energy.

There is no new related paper today

  1. [2403.08696] - On the non-perturbative bulk Hilbert space of JT gravity - Luca V. Iliesiu, Adam Levine, Henry W. Lin, Henry Maxfield, Márk Mezei

Wed - 03/13/24

There is no new related paper today

There is no new related paper today

  1. [2403.07237] - Cosmological implications from some proposals in Quantum Gravity - D. Mata-Pacheco

  2. [2403.07848] - Infinite tower of higher-curvature corrections: Quasinormal modes and late-time behavior of D-dimensional regular black holes - R. A. Konoplya, A. Zhidenko

  3. [2403.07275] - Coarse-graining black holes out of equilibrium with boundary observables on time slice - Daichi Takeda

  4. [2403.07577] - Functional renormalization group for p=2 like glassy matrices in the planar approximation: I. Vertex expansion at equilibrium - Vincent Lahoche, Dine Ousmane Samary

Tue - 03/12/24

Spinfoams, $γ$-duality and parity violation in primordial gravitational waves

  • Authors: Eugenio Bianchi, Monica Rincon-Ramirez
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2403.06053
  • Abstract The Barbero-Immirzi parameter $\gamma$ appears as a coupling constant in the spinfoam dynamics of loop quantum gravity and can be understood as a measure of gravitational parity violation via a duality rotation. We investigate an effective field theory for gravity and a scalar field, with dynamics given by a $\gamma$-dual action obtained via a duality rotation of a parity-non-violating one. The resulting relation between the coupling constants of parity-even and parity-odd higher-curvature terms is determined by $\gamma$, opening the possibility of its measurement in the semiclassical regime. For a choice of $\gamma$-dual effective action, we study cosmic inflation and show that the observation of a primordial tensor polarization, together with the tensor tilt and the tensor-to-scalar ratio, provides a measurement of the Barbero-Immirzi parameter and, therefore, of the scale of discreteness of the quantum geometry of space.

Spinfoams, $γ$-duality and parity violation in primordial gravitational waves

  • Authors: Eugenio Bianchi, Monica Rincon-Ramirez
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2403.06053
  • Abstract The Barbero-Immirzi parameter $\gamma$ appears as a coupling constant in the spinfoam dynamics of loop quantum gravity and can be understood as a measure of gravitational parity violation via a duality rotation. We investigate an effective field theory for gravity and a scalar field, with dynamics given by a $\gamma$-dual action obtained via a duality rotation of a parity-non-violating one. The resulting relation between the coupling constants of parity-even and parity-odd higher-curvature terms is determined by $\gamma$, opening the possibility of its measurement in the semiclassical regime. For a choice of $\gamma$-dual effective action, we study cosmic inflation and show that the observation of a primordial tensor polarization, together with the tensor tilt and the tensor-to-scalar ratio, provides a measurement of the Barbero-Immirzi parameter and, therefore, of the scale of discreteness of the quantum geometry of space.

Mon - 03/11/24

There is no new related paper today

A Monte Carlo algorithm for spin foam intertwiners

  • Authors: Sebastian Steinhaus
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2403.04836
  • Abstract Monte Carlo algorithms are barely considered in spin foam quantum gravity. Due to the quantum nature of spin foam amplitudes one cannot readily apply them, and the present sign problem is a threat to convergence and thus efficiency. Yet, ultimately the severity of the sign problem in spin foams is not known. In this article we propose a new probability distribution for coherent (boundary) intertwiners, which we use to define a Markov Chain Monte Carlo algorithm. We apply this algorithm to the SU(2) coherent vertex amplitude for various Regge-type boundary data and find convergent, accurate results at far lower costs than the explicit calculation. The resources are instead used to increase the size of boundary spins, bridging the gap to the asymptotic formulae. While the sign problem is not solved, it is under control in the vast majority of cases. We close by discussing how this algorithm can be extended to larger triangulations with boundary and 4d Lorentzian spin foam models. More speculatively, we discuss how this algorithm can be used to sample (Regge-geometric) bulk intertwiners.

  1. [2403.04827] - Regular Black Holes From Pure Gravity - Pablo Bueno, Pablo A. Cano, Robie A. Hennigar

  2. [2403.04826] - Circles and Triangles, the NLSM and Tr($Φ^3$) - Nima Arkani-Hamed, Carolina Figueiredo

  3. [2403.05323] - Modularity in Argyres-Douglas Theories with $a=c$ - Hongliang Jiang

New papers last week