# 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

 AMADEI Lautaro PhD candidate Email Gozzini Francesco PhD candidate Email Krajewski Thomas University faculty +33.4.91.26.95.61 Email Martin-Dussaud Pierre PhD candidate Email Martinez Daniel PhD candidate Email Perez Alejandro University faculty Chef de l’équipe « Gravité quantique » +33.4.91.26.97.98 Email Rovelli Carlo University faculty +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

### List of Publications

96 results
Preprint, Working paper
Alejandro Perez, Daniel Sudarsky, Edward Wilson-Ewing
Resolving the $H_0$ tension with diffusion
2020
Preprint, Working paper
Carlo Rovelli
Can we travel to the past? Irreversible physics along closed timelike curves
2020
Journal article
Kate Jeffery, Robert Pollack, Carlo Rovelli
On the Statistical Mechanics of Life: Schrödinger Revisited
Entropy, MDPI, 2019, 21 (12), pp.1211. ⟨10.3390/e21121211⟩
Journal article
Sergey Alexandrov, Simone Speziale
Bi-gravity with a single graviton
Journal of High Energy Physics, Springer, 2019, pp.070. ⟨10.1007/JHEP08(2019)070⟩
Journal article
Alejandro Perez, Daniel Sudarsky
Dark energy from quantum gravity discreteness
Physical Review Letters, American Physical Society, 2019, 122 (22), pp.221302. ⟨10.1103/PhysRevLett.122.221302⟩
Journal article
Lucie Laplane, Paolo Mantovani, Ralph Adolphs, Hasok Chang, Alberto Mantovani, Margaret Mcfall-Ngai, Carlo Rovelli, Elliott Sober, Thomas Pradeu
Opinion: Why science needs philosophy
Proceedings of the National Academy of Sciences of the United States of America , National Academy of Sciences, 2019, 116 (10), pp.3948-3952. ⟨10.1073/pnas.1900357116⟩
Journal article
Valerio Astuti, Marios Christodoulou, Carlo Rovelli
Volume Entropy
Classical and Quantum Gravity, IOP Publishing, 2019, 36 (5), pp.055012. ⟨10.1088/1361-6382/aafec7⟩
Journal article
Laurent Freidel, Alejandro Perez
Quantum gravity at the corner
Universe, MDPI, 2018, 4 (10), pp.107. ⟨10.3390/universe4100107⟩
Preprint, Working paper
Seramika Ariwahjoedi, Valerio Astuti, Jusak Sali Kosasih, Carlo Rovelli, Freddy Permana Zen
Statistical discrete geometry
2018
Preprint, Working paper
Goffredo Chirco, Thibaut Josset
Statistical mechanics of covariant systems with multi-fingered time
2018
96 results

February 2020 :