« TOWARDS A THEORETICAL LINK BETWEEN GRAVITATION AND QUANTUM MECHANICS »
General Relativity describes how matter* curves spacetime and how, in return, matter is influenced by this curvature—thereby explaining gravitation. Its many predictions, ranging from time dilation to gravitational waves and black holes, have been confirmed for more than a century. It therefore stands as one of the most solid pillars of modern physics.
Nevertheless, several clues suggest that General Relativity may only be the limiting case of a more complete theory. From a theoretical perspective, it notably encounters difficulties related to singularities and to the formulation of a consistent theory of quantum gravity. From an observational standpoint, recent tensions surrounding the standard cosmological model also raise questions about the completeness of our current description of the Universe. This situation is reminiscent of Newtonian gravitation, which ultimately proved to be an approximation of General Relativity.
It is in this context that a new alternative theory to General Relativity has emerged at the Observatoire de la Côte d’Azur: Entangled Relativity. This approach relies on a non-linear reformulation of the relationship between matter and spacetime curvature, making it impossible to define the theory in the absence of matter. Matter and spacetime geometry are thus “entangled” in the very formulation of the theory, in the etymological sense of the term. As a result, Entangled Relativity involves fewer fundamental constants than conventional theories, while still reproducing General Relativity as a limit or approximation in many physical regimes.
In a new publication in Classical and Quantum Gravity, researchers from the ARTEMIS laboratory of the Observatoire de la Côte d’Azur and from the Observatoire de Paris, led by Thomas Chehab, a PhD student at ARTEMIS, show that this theory has a remarkable consequence: neither the gravitational constant G nor Planck’s constant ℏ are fundamental. Both emerge as effective quantities, linked to a scalar gravitational field, and can therefore vary in space and time.
The authors quantified the amplitude of these variations in different astrophysical environments, without introducing any adjustable free parameters. Their results show that variations of G and ℏ are completely negligible in the Solar System, making Entangled Relativity indistinguishable from General Relativity at currently accessible levels of precision. By contrast, in extremely dense objects such as white dwarfs and neutron stars, these variations could become significant: of the order of one part per million for white dwarfs, and reaching a few percent inside the most compact neutron stars.
These predictions open the way to new observational tests. In particular, a variation of Planck’s constant could leave measurable signatures in the spectra of thermal radiation.
In a second publication in Physics Letters B, researchers from the ARTEMIS laboratory of the Observatoire de la Côte d’Azur and from the University of Barcelona show that the formulation of Entangled Relativity—although it may appear surprising—actually emerges as the only theory of the f(R, Lm) type, other than General Relativity, that possesses all the solutions of General Relativity for a generic type of matter.
Thus, while reproducing the experimental successes of General Relativity with high precision, Entangled Relativity leads to new predictions in regimes of extreme gravitation. It also establishes an explicit and unprecedented link between gravitation and quantum mechanics, by showing that Planck’s constant could be governed by the very structure of the gravitational field. This approach therefore opens a new avenue of exploration toward a more unified understanding of the fundamental laws of nature.
* The term “matter” is understood here in a broad sense, including the energy associated with it.
Articles :
Variation of Planck’s quantum of action in Entangled Relativity, Thomas Chehab, Olivier Minazzoli et Aurélien Hees, Classical and Quantum Gravity, 2025. https://doi.org/10.1088/1361-6382/ae30c7
Deriving Entangled Relativity, Olivier Minazzoli, Maxime Wavasseur et Thomas Chehab, Physics Letters B, 2025. https://doi.org/10.1016/j.physletb.2025.140117
Contacts :
Olivier Minazzoli leads this research at the ARTEMIS laboratory (CNRS / UMR 7250) of the Observatoire de la Côte d’Azur (OCA), within the framework of an agreement between the Government of Monaco, the CNRS, Université Côte d’Azur, and the Observatoire de la Côte d’Azur.
Contact Presse :
Margaux Arav – Head of Communications, Observatoire de la Côte d’Azur