Collection Number S005
Collection Type Series
This series consists of talks in the area of Quantum Gravity.

Asymptotics of the eprl model on arbitrary vertices

Simone Speziale Centre de Physique Théorique (CPT)

We introduce a new technique to study the critical point equations of the eprl model. We show that it correctly reproduces the 4-simplex asymptotics, and how to apply it to an arbitrary vertex. We find that for general vertices, the asymptotics can be linked to a Regge action for polytopes, but contain also more general geometries, called conformal twisted geometries. We present explicit examples including the hypercube, and discuss implications.

LQG in diagonal gauge: A modern approach

Gioele Botta University of Warsaw

The full theory of LQG presents enormous challenge to create physical computable models. In this talk we will present the new modern version of Quantum Reduced Loop Gravity. We will show that this framework provide an arena to study the full LQG in a certain limit, where the quantum computations are possible. We will analyze all the major step necessary to build this framework, how is connected with the full theory, its mathematical consistency and the physical intuition behind It.

Quantum-reduced loop gravity from the perspective of full LQG

Ilkka Mäkinen University of Warsaw

Quantum-reduced loop gravity is a model of loop quantum gravity, whose characteristic feature is the considerable simplicity of its kinematical structure in comparison with that of full loop quantum gravity. The model therefore provides an accessible testing ground for probing the physical implications of loop quantum gravity. In my talk I will give a brief introduction to quantum-reduced loop gravity, and examine the relation between the quantum-reduced model and full loop quantum gravity.

Covariant Loop Quantum Gravity, the State of the Art

Carlo Rovelli Centre de Physique Théorique (CPT)

The covariant (spinfoam) formulation of loop gravity is a tentative physical quantum theory of gravity with well defined transition amplitudes.  I give my current understanding of the state of the art in this research direction, the issues that are open and need to be explored, and the current attempts to use the theory to compute quantum effects in the early universe and in black hole physics.

Quantum group in 3d quantum gravity

Florian Girelli University of Waterloo

It is well-known that quantum groups are relevant to describe the quantum regime of 3d gravity. They encode a deformation of the gauge symmetries (Lorentz symmetries) parametrized by the value of the cosmological constant. They appear as some kind of regularization either through the quantization of the Chern-Simons formulation (Fock-Rosly formulation/combinatorial quantization, path integral quantization) or the state sum approach (Turaev-Viro model). Such deformation might be perplexing from a classical picture since the action is defined in terms of plain/undeformed gauge symmetry.

Gravitational edge modes: From Kac-Moody charges to Poincaré networks

Daniele Pranzetti Perimeter Institute for Theoretical Physics

In this talk I revisit the canonical framework for general relativity in its connection-frame field formulation, exploiting its local holographic nature. I will show how we can understand  the  Gauss law, the Bianchi identity and the space diffeomorphism constraints as conservation laws for local surface charges. These charges being respectively the electric flux, the dual magnetic flux  and momentum charges. Quantization of the surface charge algebra can be done in terms of Kac-Moody edge modes.

The quasi-local degrees of freedom of Yang-Mills theory

Gauge theories possess nonlocal features that, in the presence of boundaries, inevitably lead to subtleties. In particular their fundamental degrees of freedom are not point-like. This leads to a non-trivial cutting (C) and sewing (S) problem: 
(C) Which gauge invariant degrees of freedom are associated to a region with boundaries? 

Quantum Geometry vs. Quantum Gravity

Bianca Dittrich Perimeter Institute for Theoretical Physics

Quantizing 4D geometries leads to discrete area spectra. Such discrete area spectra are also suggested by the holographic principle and entropy counting for black holes.

The trinity of relational quantum dynamics

Philipp Hoehn Okinawa Institute of Science and Technology (OIST)

In order to solve the problem of time in quantum gravity, various approaches to a relational quantum dynamics have been proposed. In this talk, I will exploit quantum reduction maps to illustrate a previously unknown equivalence between three of the well-known ones: (1) relational observables in the clock-neutral picture of Dirac quantization, (2) Page and Wootters’ (PW) Schrödinger picture formalism, and (3) the relational Heisenberg picture obtained via symmetry reduction. Constituting three faces of the same dynamics, we call this equivalence the trinity.