# 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

 Krajewski Thomas University faculty +33.4.91.26.95.53 Email MUNCH Johannes Postdoctoral researcher Email ODAK Gloria PhD candidate Email Perez Alejandro University faculty Chef de l’équipe « Gravité quantique » +33.4.91.26.97.98 Email RIBISI Salvatore PhD candidate Email RIGNON BRET Antoine PhD candidate +33.4.91.26.95.57 Email Rovelli Carlo Emeritus +33.4.91.26.96.44 Email Speziale Simone Researcher Chef du Groupe « Interactions fondamentales » +33.4.91.26.95.47 Email VIOLLET Sami PhD candidate +33.4.91.26.95.56 Email

### List of Publications

102 results
Journal article
Sergey Alexandrov, Simone Speziale, Tom Zlosnik
Canonical structure of minimal varying $\Lambda$ theories
Classical and Quantum Gravity, IOP Publishing, 2021, 38 (17), pp.175011. ⟨10.1088/1361-6382/ac1852⟩
Journal article
Goffredo Chirco, Thibaut Josset
Statistical mechanics of covariant systems with multi-fingered time
Foundations of Physics, Springer Verlag, 2021, 51, pp.3. ⟨10.1007/s10701-021-00406-3⟩
Journal article
Alejandro Perez, Daniel Sudarsky, Edward Wilson-Ewing
Resolving the $H_0$ tension with diffusion
General Relativity and Gravitation, Springer Verlag, 2021, 53, pp.7. ⟨10.1007/s10714-020-02781-0⟩
Journal article
Andrea Calcinari, Laurent Freidel, Etera R. Livine, Simone Speziale
Twisted Geometries Coherent States for Loop Quantum Gravity
Classical and Quantum Gravity, IOP Publishing, 2021, 38 (2), pp.025004. ⟨10.1088/1361-6382/abc273⟩
Journal article
Roberto Oliveri, Simone Speziale
A note on dual gravitational charges
Journal of High Energy Physics, Springer, 2020, 2020, pp.79. ⟨10.1007/JHEP12(2020)079⟩
Journal article
Kate Jeffery, Carlo Rovelli
Transitions in Brain Evolution: Space, Time and Entropy
Trends in Neurosciences, Elsevier, 2020, 43 (7), pp.467-474. ⟨10.1016/j.tins.2020.04.008⟩
Journal article
Denise Cocchiarella, Stefano Scali, Salvatore Ribisi, Bianca Nardi, Ghofrane Bel-Hadj-Aissa, Roberto Franzosi
Entanglement distance for arbitrary M -qudit hybrid systems
Physical Review A, American Physical Society 2020, 101 (4), pp.042129. ⟨10.1103/PhysRevA.101.042129⟩
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⟩
102 results

## Calendar

October 2021 :

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