# 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 SAUL Andres Guest Email Speziale Simone Researcher +33.4.91.26.95.46 Email Vidotto Francesca Guest Email

### List of Publications

83 results
Book Section
J. Fernando Barbero G., Alejandro Perez
Quantum Geometry and Black Holes
A. Ashtekar; J. Pullin. Loop Quantum Gravity : The First 30 Years , 4, World Scientific, pp.241-279, 2017, 100 Years of General Relativity, 978-981-3209-92-3. 〈10.1142/9789813220003_0008〉
Journal article
Laurent Freidel, Alejandro Perez, Daniele Pranzetti
The loop gravity string
Physical Review D, American Physical Society, 2017, 95 (10), pp.106002. 〈10.1103/PhysRevD.95.106002〉
Journal article
Alberto S. Cattaneo, Alejandro Perez
A note on the Poisson bracket of 2d smeared fluxes in loop quantum gravity
Classical and Quantum Gravity, IOP Publishing, 2017, 34 (10), pp.107001. 〈10.1088/1361-6382/aa69b4〉
Preprint, Working paper
Goffredo Chirco, Thibaut Josset
Statistical mechanics of covariant systems with multi-fingered time
2017
Preprint, Working paper
Valerio Astuti, Marios Christodoulou, Carlo Rovelli
Volume Entropy
2017
Preprint, Working paper
L. Rosa, S. Avino, E. Calloni, S. Caprara, M. De Laurentis, R. De Rosa, Giampiero Esposito, M. Grilli, E. Majorana, G. P. Pepe, S. Petrarca, P. Puppo, P. Rapagani, F. Ricci, C. Rovelli, P. Ruggi, N. L. Saini, C. Stornaiolo, F. Tafuri
Casimir energy for two and three superconducting coupled cavities: numerical calculations
2017
Preprint, Working paper
Seramika Ariwahjoedi, Valerio Astuti, Jusak Sali Kosasih, Carlo Rovelli, Freddy Permana Zen
Statistical discrete geometry
2017
Journal article
Hongguang Liu, Xin Wang, Haida Li, Yongge Ma
Distinguishing $f(R)$ theories from general relativity by gravitational lensing effect
Eur.Phys.J.C, 2017, 77 (11), pp.723. 〈10.1140/epjc/s10052-017-5308-5〉
Journal article
Simone Speziale
Boosting Wigner's nj-symbols
Journal of Mathematical Physics, American Institute of Physics (AIP), 2017
Journal article
Thibaut Josset, Alejandro Perez, Daniel Sudarsky
Dark Energy from Violation of Energy Conservation
Physical Review Letters, American Physical Society, 2017, 118 (2), pp.021102 〈10.1103/PhysRevLett.118.021102〉
83 results

November 2017 :