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Seminario di Dipartimento: Interpretation of Quantum Theory, Cosmology and Gravitation


Physics Department seminar
AULA A in presence and streaming
28 Aprile 2023– 14:30
Prof. Giovanni Prosperi
Università degli Studi di Milano

Interpretation of Quantum Theory, Cosmology and Gravitation

We reconsider the problem of the interpretation of the Quantum Theory (QT) in the perspective of the entire Universe and of Bohr idea that the classical language is the language of our experience and QT acquires a meaning only with a reference to it.
We distinguish a classical or macroscopic level, and a quantum or microscopic one that is perceived only through the modifications that it induces in the first. The macroscopic state of the Universe is assumed to be specified by a set of variables, a classical energy momentum tensor and some conserved currents, which are supposed to have a well defined value across the entire space-time. To the energy-momentum tensor a classical metric is related by the Einstein equation. The quantum state and dynamics are expressed by the usual QT formalism in terms of a density operator and the ordinary quantum operators in Heisenberg picture. For the macroscopic variables a basic distribution of probability is postulated in terms of a density and the corresponding quantum operators, so in some way their evolution is driven by the underlying QT. Such postulate essentially replaces the usual selfadjoint operators correspondence. For the Universe we adopt a variance of the ΛCDM model with Ω=1, one single inflaton with an Higgs type potential, the initial time at t=-∞. The expectation values of all fundamental fields are supposed
to vanish for t→-∞ .
In the framework the scalar fluctuation in the Cosmic Microwave Background are correctly explained giving appropriate value to the parameters in the potential. As in more conventional models the absence of the tensor fluctuations remains not understood, if even a quantum metric is introduced. This seems to suggest that Gravity is a pure classical phenomenon, what could be consistently accommodated in our
formalism by an appropriate even if somewhat ad hoc assumption.

Students are cordially invited – Contact silvia.leoni@mi.infn.it


28 aprile 2023
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