### Conveners

#### Loop Quantum Gravity: Block 1

- Jerzy Lewandowski (Uniwersytet Warszawski)
- Marcin Kisielowski (National Centre for Nuclear Research, Poland)

#### Loop Quantum Gravity: Block 2

- Jerzy Lewandowski (Uniwersytet Warszawski)
- Marcin Kisielowski (National Centre for Nuclear Research, Poland)

### Description

Loop quantum gravity is a background independent, non-perturbative approach to quantum gravity. The focus of this session is on the structure of the theory, its computational techniques and applications to cosmology and black hole physics. We welcome talks reporting recent developments in canonical loop quantum gravity, spin-foam models, group field theory and related approaches to quantum gravity. The common theme is the background independent quantization of Einstein's gravity and the occurrence of quantum geometry. Loop quantum cosmology and reduced quantum models of black holes will be discussed in the separate session QG3.

Current Lorentzian Spinfoams are formulated in terms of a two-complex with spins on faces and intertwiners on edges. In this talk, I discuss how to add a causal structure on wedges. The EPRL model turns out to be given by a sum over these wedge-causal structures. I will show how this sum can be restricted to a single causal configuration and its relation to Engle's proper vertex. [Based on...

The Lorentzian EPRL spin-foam model has been shown to asymptote in an appropriate regime to a Regge-like theory of gravity. Analogous results have recently been obtained for the Conrady-Hnybida (CH) extension of the model, but several questions regarding the amplitudes of time-like triangles remain open. In this talk I will present new progress on the asymptotic analysis of such amplitudes, in...

Black holes formation and evolution have been extensively studied at the classical level. However, not much is known regarding the end of their lives, a phase that requires to consider the quantum nature of the gravitational field. A black-to-white hole transition can capture the physics of this phenomenon, in particular the physics of the residual small black holes at the end of the Hawking...

The application of numerical techniques to covariant LQG may able to provide answers to many of the current open questions in theory. In this presentation, I first introduce the formalism currently used to implement numerical computations. I illustrate a recent application of numerical techniques concerning the study of divergences in the EPRL self-energy amplitude, on which so far there were...

This talk describes how the Barbero--Immirzi parameter deforms the SL(2,R) symmetries on a null surface boundary. Our starting point is the definition of the action and its boundary terms. We introduce the covariant phase space and explain how the Holst term alters the symmetries on a null surface. This alteration only affects the algebra of the edge modes on a cross-section of the null...

Gravity admits several formulations. Some of the most well-known are standard GR and Palatini both in tetrad and metric formulation. In this talk, I will show the equivalence, in the covariant Phase Space, of all four formulations on a spacetime manifold with boundary. To this end, we will rely on the cohomological approach provided by the relative bicomplex framework.

It is reasonable to think that the spin labels of spin networks have nothing to do with physical rotation or spin. However, intriguingly, in situations involving rotating black holes, a connection between the spin of spin networks and angular momentum has been established. Here I want to consider this connection from another angle: Can we talk about the spin of fermions in loop quantum...

Loop quantum gravity (LQG) in its current formulation is a the quantisation of the SU(2) gauge theory of gravity in Ashtekar-Barbero variables. It started out as an SL(2,C) gauge theory in Ashtekar's selfdual variables, but the quantisation program was never fully carried out in this formulation. The two main obstacles are the non-compactness of the gauge group SL(2,C) and the necessity to...

This talk is devoted to the quantization of supergravity in a formulation in which (part of) supersymmetry manifests itself in terms of a gauge symmetry. Applications we have in mind are supersymmetric black holes and loop quantum cosmology.

We will derive the Holst variant of the MacDowell-Mansouri action for $\mathcal{N}=1$ and $\mathcal{N}=2$ supergravity in $D=4$ for arbitrary...

Given the Loop-Quantum-Gravity (LQG) non-graph-changing Hamiltonian $\widehat{H[N]}$, the coherent state expectation value $\langle\widehat{H[N]}\rangle$ admits an semiclassical expansion in $\ell^2_{\rm p}$. In this paper, we compute explicitly the expansion of $\langle\widehat{H[N]}\rangle$ on the cubic graph to the linear order in $\ell^2_{\rm p}$, when the coherent state is peaked at the...

We define bulk-to-boundary maps corresponding to quantum gravity states in the tensorial group field theory formalism, for quantum geometric models sharing the same type of quantum states of loop quantum gravity. The maps are defined in terms of a partition of the quantum geometric data associated to an open graph into bulk and boundary ones, in the spin representation. After showing that such...

I discuss the simplest solution of the covariant Schroedinger equation of

quantum gravitational field derived using precanonical quantization,

a quantization based on the De Donder-Weyl Hamiltonian theory which

requires no space-time decomposition. This is a second-order PDE for

a Clifford algebra valued wave function on the space of space-time and spin-connection variables which...