### Conveners

#### Loop Quantum Gravity: Cosmology and Black Holes: Block 2

- Parampreet Singh (Louisiana State University)
- Jorge Pullin (Louisiana State University)

#### Loop Quantum Gravity: Cosmology and Black Holes: Block 1

- Jorge Pullin (Louisiana State University)
- Parampreet Singh (Louisiana State University)

### Description

Non-perturbative quantum gravity effects as understood from loop quantum gravity and related approaches play an important role in resolution of singularities of cosmological and black hole spacetimes, and leave potential signatures in the physics of early universe and black hole spacetimes. The goal of this session would be to highlight state of the art of various developments in this field with talks focused on physical implications.

In this talk, we shall present our studies of a recently-proposed model of spherically symmetric polymer black/white holes by Bodendorfer, Mele

and M\"unch (BMM), which generically possesses five free parameters. However, we find that, out of these five parameters, only three independent combinations

of them are physical and uniquely

determine the local and global properties of the...

We study the mode decomposition of the unitarily evolving wave packet constructed for the quantum model of spherically symmetric dust collapsing in marginally bound Lemaître-Tolman-Bondi (LTB) model. We consider the model developed by Kiefer et al. [Phys.Rev.D 99 (2019) 12, 126010], where black hole singularity is replaced by a bounce from collapsing phase to expanding phase in the quantum...

The idea that, after their evaporation, Planck-mass black holes might tunnel into metastable white holes has recently been intensively studied. Those relics have been considered as a dark matter candidate. We show that the model is severely constrained and underline some possible detection paths. We also investigate, in a more general setting, the way the initial black hole mass spectrum would...

We study some consequences of the loop quantization of the outermost shell in the Lema\^itre–Tolman–Bondi (LTB) dust spacetime using different quantization strategies motivated by loop quantum gravity. Prior work has dealt with this loop quantization by employing holonomies and the triads, following the procedure in standard loop quantum cosmology. In this work we compare this quantization...

We develop a systematic approach to obtain spherically symmetric midisuperspace models with modifications inherited from loop quantum gravity. We obtain a family of effective constraints that satisfy Dirac's deformation algebra and show that (scale-dependent) holonomy corrections can be consistently implemented in the presence of matter with local degrees of freedom. These deformed...

The interior of a Schwarzschild black hole is quantized by the method of loop quantum gravity. The Hamiltonian constraint is solved and the physical Hilbert space is obtained in the model. The properties of a Dirac observable corresponding to the Arnowitt-Deser-Misner mass of the Schwarzschild black hole are studied by both analytical and numerical techniques. It turns out that zero is not in...

In this talk, I will present the main features of the solutions to a recently-derived set of dynamical equations that governs the effective dynamics of black holes in loop quantum cosmology which were obtained via a revision of the Hamiltonian calculation underlying the Ashtekar-Olmedo-Singh black hole model. I will analyze the possibility that certain quantum parameters are treated as Dirac...

We show that loop quantization leads to the emergence of defocusing terms in the expansion and its rate of change, the Raychaudhuri equation. These terms are suppressed in the region far from the singularity but dominate close to that region and prevent both the expansion and its rate from diverging everywhere inside the black hole. This in turn signals the disappearance of the caustic points...

In traditional (Dirac quantized) quantum mechanics, Gaussian wave functions play an important role in understanding semi-classicality: they may be chosen to be as sharply-peaked around classical position coordinates and they saturate the uncertainty relation, thereby minimizing quantum fluctuations. Gaussian states may likewise be constructed on the kinematic volume Hilbert space of loop...

The PLANCK satellite has observed certain anomalies in the Cosmic Microwave Background (CMB) that bring out a tension between the standard six-parameter $\Lambda$CDM cosmological model and observations. The possibility that these anomalies could be tell-tale signatures of fundamental physics at the Planck scale is exciting. We show that this possibility is realized within Loop Quantum...

A union of matter bounce and ekpyrotic scenarios is often studied in an attempt to combine the most promising features of these two models. Since nonperturbative quantum geometric effects in loop quantum cosmology (LQC) result in natural bouncing scenarios without any violation of energy conditions or fine tuning, an investigation of matter-ekpyrotic bounce scenario is interesting to explore...

In this talk we discuss three different models for a reduced phase space quantization of loop quantum cosmology (LQC) for a spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) universe filled with reference fields and an inflaton field in a Starobinsky inflationary potential. All three models are two-fluid models and they differ by their choice of global clock which are chosen to be...

There is an increasing interest in very early stages of the Universe in which the energy density of the inflaton could be dominated by its kinetic part. This includes classical inflationary scenarios with deviations from slow-roll regimes that can introduce modifications to the power spectra of the primordial fluctuations. Another example are quantum bouncing cosmologies. For instance, this is...

The initial conditions are a subtle issue in loop quantum cosmology (LQC) and modified loop quantum cosmologies (mLQCs). This is mainly because in general there doesn't exist a preferred initial time and state for a quantum field in an arbitrarily curved space-time. If the universe is sufficiently smooth and its evolution is sufficiently slow, so the characteristic scale of perturbations...

The paradigm of slow-roll inflation provides a snapshot of the early universe that is in good agreement with present observations. Despite its success, most of the models studied so far rely heavily on the assumption that the universe is perfectly isotropic at early times. In this talk, I will discuss recent advances in anisotropic inflationary models. We adopt a Fock quantization for...

In the talk, I will discuss the primordial power spectra in two modified models of loop cosmology. As compared with the standard loop quantum cosmology in a spatially flat Friedmann-Lema\^itre-Robertson-Walker (FLRW) universe, these two models arise from a separate treatment of the Lorentzian term in the Hamiltonian constraint. Both dressed metric approach and the hybrid approach are employed...

We propose a cosmological model that can provide a common origin to several of the anomalous features observed at large angular scales in the cosmic microwave background (CMB). More concretely, we show that a power suppression, a dipolar asymmetry, and a preference for odd-parity correlations, with amplitude and scale dependence in consonance with observations, are expected from this scenario....

In this talk we will review the known result that the background evolution of standard LQC can be reproduced by a covariant metric-affine f(R) theory all the way up to bounce curvatures. We will then show that other Loop Cosmologies dubbed as mLQC-I and mLQC-II, differing on standard LQC due to quantisation ambiguities related to the Lorentzian term of the Hamiltonian, also admit covariant...

In the framework of reduced phase space Loop Quantum Gravity (LQG), we propose a new approach in coherent state path integral formulation which allows the spatial cubic lattice (graph) to change dynamically in the physical time evolution. The equations of motion of the path integral derive the effective dynamics of cosmology from the full LQG, when we focus on solutions with homogeneous and...

Increasing theoretical evidence supports the possibility that quantum theory replaces the black hole singularity with a quantum tunnelling to an anti-trapped region, and the blackhole horizon tunnels into a white hole horizon. I review the different elements supporting this intriguing scenario, and mention its possible astrophysical and cosmological implications.