# Centre de Physique Théorique

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# Quantum Gravity

###### Group “Fundamental Interactions”

The QG equipe works on a major unsolved question in fundamental physics: understanding the quantum properties of gravity. Since gravity is the dynamics of spacetime, this amount to study the quantum behaviour of time and space.

Loop Quantum Gravity (LQG), is a main approach towards the solution of this problem, and the CPT is a leader in this field. The group works on the formal definition of the theory, its mathematical aspects, and its applications.

Among the formal developments, the group is studying the properties of the coherent semiclassical states which describe quantum geometry, and is developing a reformulation of the theory in terms of twistors which should simplify its application.

The main applications are to early cosmology and to black hole physics. The objective of the research is to find observable phenomena that could test the theory empirically.

In the context of early cosmology, LQG allows to explore the region around the initial singularity predicted by classical general relativity. The theory indicates that the present expansion phase was preceded by a contraction phase.

In the context of Black hole physics, LQG opens the possibility to study the physics of the high-curvature region (the “Planck star”), suggesting that the singularity predicted by classical general relativity is cured by quantum effects. A black hole is consequently unstable: it can explode via a quantum tunnelling process, akin to conventional radioactive nuclear decay. The equipe studies the signals produced by such black hole explosions. One hypothesis is that currently observed astrophysical phenomena such as very-high-energy gamma rays or Fast Radio Bursts could be originated by such a quantum gravitational explosion of primordial black holes.

The quantum structure of spacetime is also relevant for the thermal properties of the black holes and for the so-called black-hole “information paradox”. The group is at the forefront of the analysis of these questions.

### Directory of Members

 D’Ambrosio Fabio PhD candidate Email De Lorenzo Tommaso PhD candidate Email Krajewski Thomas University faculty +33.4.91.26.95.61 Email Liu Hongguang PhD candidate Email Martin-Dussaud Pierre PhD candidate Email Martinez Daniel PhD candidate Email Perez Alejandro University faculty +33.4.91.26.97.98 Email Rovelli Carlo University faculty Chef de l’équipe « Gravité quantique » +33.4.91.26.96.44 Email SARNO Giorgio PhD candidate Email Saul Andres Guest Email Speziale Simone Researcher +33.4.91.26.95.46 Email Vidotto Francesca Guest Email

### List of Publications

86 results
Journal article
Miklos Långvik, Simone Speziale
Twisted geometries, twistors and conformal transformations
Physical Review D, American Physical Society, 2016, 94 (2)
Conference paper
Carlo Rovelli
The dangers of non-empirical confirmation
String Theory and the Scientific Method, Dec 2015, Munich, Germany. 2016
Conference paper
Thomas Krajewski, Reiko Toriumi
Power counting ans scaling for tensor models
School and Workshops on Elementary Particle Physics and Gravity, Sep 2015, Corfou, Greece. Corfu Summer Institute 2015 (116), 2015, Proceedings of Science
Conference paper
Gerard 'T Hooft, Steven B. Giddings, Carlo Rovelli, Piero Nicolini, Jonas Mureika, Matthias Kaminski, Marcus Bleicher
The Good, the Bad, and the Ugly of Gravity and Information
2nd Karl Schwarzschild Meeting, Jul 2015, Frankfurt am Main, Germany. 2016
Journal article
Eugenio Bianchi, Tommaso De Lorenzo, Matteo Smerlak
Entanglement entropy production in gravitational collapse: covariant regularization and solvable models
Journal of High Energy Physics, Springer, 2015, 2015 (6), 〈10.1007/JHEP06(2015)180〉
Journal article
Carlo Rovelli
The strange equation of quantum gravity
Classical and Quantum Gravity, IOP Publishing, 2015, 32, pp.124005
Book
Carlo Rovelli
General Relativity. The Most beautiful of Theories.
De Gruyter, pp.208, 2015, 978-3-11-038364-5, 978-3-11-038364-5
Journal article
Carlo Rovelli
Aristotle’s Physics: A Physicist’s look
Journal of the American Philosophical Association, Cambridge Journals, 2015, 1 (1), pp.23-40. 〈10.1017/apa.2014.11〉
Journal article
Joseph Ben Geloun, Reiko Toriumi
Parametric Representation of Rank d Tensorial Group Field Theory: Abelian Models with Kinetic Term $\sum_{s}|p_s| + \mu$
Journal of Mathematical Physics, American Institute of Physics (AIP), 2015, 56 (9), pp.093503. 〈10.1063/1.4929771〉
Journal article
Alejandro Perez
No firewalls in quantum gravity: the role of discreteness of quantum geometry in resolving the information loss paradox
Classical and Quantum Gravity, IOP Publishing, 2015, Focus Issue: Entanglement and Quantum Gravity, 32 (8), pp.084001. 〈10.1088/0264-9381/32/8/084001〉
86 results

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