FAU^2 Mini-Workshop on Loop Quantum Gravity

Contribution List

6. Symmetry charges in reduced phase space and their algebra

Hongwei Tan

02/05/2023, 14:15

Session 1

The investigation of boundary charges in asymptotically flat spacetime drew a lot of attention in recent years, which has provided us valuable insight and significantly enhanced our general understanding of gravity. However, most of previous studies along this line are based on the traditional general relativity, which is a pure constraint theory in the bulk. The boundary charges based on the...

3. Edge modes and quantum reference frames in linearized gravity

Wolfgang Wieland

02/05/2023, 15:15

Session 1

A common way to interpret the coordinate invariance of Einstein’s equations is to say that coordinates are a mere gauge redundancy and play no physical role themselves. This is no longer true when we restrict ourselves to subsystems localized in a compact but otherwise arbitrary domain. At the boundary of the domain, coordinate transformations are no longer gauge redundant. The then necessary...

1. A master equation for gravitationally induced decoherence of a scalar field using Ashtekar variables

Max Joseph Fahn

02/05/2023, 16:45

Session 2

In the talk, we present the derivation of a decoherence model
containing a scalar field coupled to a gravitational environment. With such models the influence of the quantum gravitational environment on the scalar field’s dynamics can be analysed. Starting with full general relativity in Ashtekar's connection formulation, we focus on weak gravitational interactions in an asymptotically flat...

7. Early Dark Energy: a status update and new constraints using the profile likelihood

Laura Herold

03/05/2023, 13:30

Session 3

Early dark energy (EDE) is a dark energy-like component in the early universe, which was proposed to solve the Hubble tension, a discrepancy between different measurements of the current expansion rate of the universe. Currently, there is no consensus in the literature as to whether EDE can simultaneously solve the Hubble tension and provide an adequate fit to the data from the cosmic...

4. Radiative correction of 4D spinfoam model with a cosmological constant

Qiaoyin Pan

03/05/2023, 14:30

Session 3

Infrared divergence is a common feature of spinfoam models with a vanishing cosmological constant. The disappearance of divergence at the present of a non-zero cosmological constant was conjectured and then recently proved in a spinfoam model constructed with complex Chern-Simons theory. It has been an active research area to study how such divergence depends on the value of the cosmological...

5. Complex critical point and effective dynamics of spinfoam quantum gravity

Dongxue Qu

03/05/2023, 16:00

Session 4

This talk will be based on the paper arXiv:2301.02930. I will introduce the complex critical points in the 4-dimensional Lorentzian Engle-Pereira-Rovelli-Livine (EPRL) spinfoam model in the large-$j$ regime. For the 4-simplex amplitude, taking into account the complex critical point generalizes the large-$j$ asymptotics to the situation with non-Regge boundary data and relates to the twisted...

2. On consistent gauge-fixing conditions in polymerized gravitational systems

Stefan Weigl

03/05/2023, 17:00

Session 4

Gauge fixing is a standard method for deriving the physical sector of a gauge theory. In the context of symmetry reduced models of loop quantum gravity a polymerisation has been applied to gauge fixed models to obtain so called effective theories that mimic the underlying quantum theory to some extend. Motivated from the question whether gauge fixing and polymerization commute, in this talk we...