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.
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Eugenio Bianchi (Penn State)05/07/2021, 16:30Loop Quantum GravityTalk in the parallel session
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...
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José Diogo Simão (Theoretical Physics Institute Jena)05/07/2021, 17:00Loop Quantum GravityTalk in the parallel session
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...
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Farshid Soltani (Western U., Canada)05/07/2021, 17:30Loop Quantum GravityTalk in the parallel session
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...
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Pietropaolo Frisoni (Western University)05/07/2021, 18:00Loop Quantum GravityTalk in the parallel session
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...
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Wolfgang Wieland (Institute for Quantum Optics and Quantum Information (IQOQI, Vienna))05/07/2021, 18:30Loop Quantum GravityTalk in the parallel session
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...
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Juan Margalef (PSU)05/07/2021, 19:00Loop Quantum GravityTalk in the parallel session
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.
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Hanno Sahlmann (Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU))07/07/2021, 09:30Loop Quantum GravityTalk in the parallel session
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...
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Robert Seeger (Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU))07/07/2021, 10:00Loop Quantum GravityTalk in the parallel session
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...
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Konstantin Eder (Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU))07/07/2021, 10:30Loop Quantum GravityTalk in the parallel session
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...
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Cong Zhang (University of Warsaw)07/07/2021, 11:00Loop Quantum GravityTalk in the parallel session
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...
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Eugenia Colafranceschi (University of Nottingham)07/07/2021, 11:30Loop Quantum GravityTalk in the parallel session
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...
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Igor Kanatchikov (Natl Quantum Information Center)07/07/2021, 12:00Loop Quantum GravityTalk in the parallel session
I discuss the simplest solution of the covariant Schroedinger equation of
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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...