**Rethinking the link between matter and geometry**

The theory of General Relativity relates gravitational phenomena (e.g. free fall, the expansion of the universe, etc.) to “space-time” curvature. However, in order to derive its final equation, Albert Einstein had to use “guiding principles”, such as the Equivalence Principle – which enforces the universality of free fall. From a practical perspective, it is consistent to the fact that a violation of the universality of free fall has never been observed, even more than a century after postulating his theory. Nevertheless, several theoretical physicists already argued that the Equivalence Principle should not be regarded as a fundamental principle.

In an article recently published in

*Physical Review*, “

*Rethinking the link between matter and geometry”,*Dr. Minazzoli presents a new theory that does not possess new ingredients with respect to general relativity, but which is based on a novel guiding principle – which enforces that matter and geometry cannot be described separately; while it says nothing on the universality of free falls.

Surprisingly, not only does the theory have a dynamics that seems consistent with observations, but features usually expected from the Equivalence Principle would be explained by the specific evolution of the universe after the big bang – instead of being postulated as in general relativity.

Nevertheless, many studies remain to be done in order to quantitatively estimate its validity. In particular, a strong requirement would be that this new theory could solve issues usually related to “quantum gravity”.