Conveners
Loop quantum gravity: cosmology and black holes: Tuesday block 1
- Jorge Pullin (Louisiana State University)
- Parampreet Singh (Louisiana State University)
Loop quantum gravity: cosmology and black holes: Tuesday block 2
- Parampreet Singh (Louisiana State University)
- Jorge Pullin (Louisiana State University)
Description
Session on loop quantum gravity concentrating on developments in black holes and cosmologies.
Gravitational waves propagate at the speed of light. If we take an ultra-short distributional pulse of gravitational radiation, the resulting wavefront will move along a co-dimension one light-like (null) surface in spacetime. The question of how to describe the quantum geometry of such impulsive null initial data is an important physical problem shared across different approaches. In my...
In this talk we present the analysis of the embedding of a large class of generalized LTB models in effective spherically symmetric spacetimes. We introduce a reconstruction algorithm that allows, for a large class of models, to construct from a given metric in Schwarzschild-like coordinates the corresponding effective spherically symmetric model, its dynamics as a 1+1-dimensional field...
I will present the quantum evolution of scalar field modes on a quantum spacetime of a collapsing, homogeneous dust ball. Without field backreaction, quantum gravity resolves classical singularities, causing a bounce on the collapse background. Including backreaction, the emergent dressed geometry becomes mode-dependent, resembling a radiation fluid. I will examine the semiclassical dynamics...
One of principal aspects in which the effects of quantum gravity are hoped to manifest itself through possible modification to a dispersion relation of electromagnetic (e-m) waves. By combining (i) the symmetry reduced approaches to spacetime quantization, including loop quantum cosmology or geometrodynamics framework, and (ii) the (extension of the) Born-Oppenheimer approximation of...
Observations by Planck indicate that CMB anisotropies are consistent with predictions of nearly Gaussian primordial perturbations as the one generated in slow roll inflation. On the other hand, loop quantum cosmology (LQC) generates a non-Gaussian bispectrum. In particular, calculations of primordial bispectrum generated in LQC shows that the non-Gaussianity function $f_{_{\rm NL}}(k_1,\,...
The collapse of a spherically symmetric ball of dust has been intensively studied in Loop Quantum Gravity (LQG). From a quantum theory, it is possible to recover a semiclassical regime through a polymerization procedure. In this setting, general solutions to the Polymerized Einstein Field Equations (PEFE) will be discussed both for the interior and the exterior of the dust cloud. Exterior...
Effective models of gravitational collapse in loop quantum gravity for the Lemaître-Tolman-Bondi spacetime predict that collapsing matter reaches a maximum finite density, bounces, and then expands outwards. I explain how in the marginally bound case, shell-crossing singularities commonly occur for inhomogeneous initial profiles of the dust energy density; this is the case in particular for...
In this talk, we aim to discuss the abelian features of Loop Quantum Cosmology, demonstrating that the Gauss constraint can be recast into three abelian constraints.
We begin the discussion by considering nondiagonal Bianchi models, illustrating their deep connection with the diagonal case. Specifically, we show that the Hilbert space of these models factorizes into spaces that are isomorphic...
A common criticism to deparametrised quantum gravity formalisms, where a time variable is selected before quantisation, is that covariance seems to be lost. In this talk, I will resolve this concern for the group field theory (GFT) approach to quantum gravity thanks to the equivalence between the Dirac quantisation scheme and the Page-Wootters (PW) formalism — applied here to quantum gravity...
