Carlo Rovelli

CPT Marseille
Quantum events as the basis of quantum mechanics and quantum gravity

Most basic physics concepts, such as classical space and time, particles, fields, energy-momentum ..., lose their meaning, or require severe revision, in the regimes where quantum gravity phenomena are become non-negligible. The notion of "event" does not, and may represent the central concept on which the theory of quantum gravity can be constructed. Events are "happenings of something somewhere at some time". This scant conceptual structure may be sufficient to ground a theory of quantum spacetime. The aim of this project is to develop such a foundation and to test it in a concrete calculation: computing the time for a black hole to explode via a non perturbative quantum process. If events can be taken as the elementary n of physics, we seem to be forced to understand identity across time only as a secondary notion. Processes, rather than individuals, structure the world, as i the famous Wittgenstein’s Tractatus incipit "The world is the totality of the facts,
not of things".

The PI has been developing an interpretation of quantum mechanics called the Relational Interpretation, based on the notion of quantum event. This research has been developed independently from the PI's main work, which is on quantum gravity, focused on the Loop approach. The present project aims at merging the quantum event interpretation of quantum theory with quantum gravity. The advantage of the event interpretation is that it should remain meaningful in quantum gravity, where most basic conventional physical notions require revision. The notion of quantum event offers a possible basis for the foundation of the theory. This is because something intriguing happens in this context: the network of interacting quantum events can be identified with the very fabric that weaves spacetime. First aim of this project is to clarify the conceptual structure underpinning a non-perturbative formulation of quantum gravity in terms of relational events. Second aim is to test this conceptual structure in a concrete physical situation: the calculation of the tunnelling time for a Hájíček-Kiefer transition from a black hole to a white hole geometry.

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