Berlin 2018 – wissenschaftliches Programm

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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 5: Philosophie der Physik IV

AGPhil 5.4: Vortrag

Freitag, 16. März 2018, 11:30–12:00, H 2033

The Emergence of the Classical World from a Bohmian Universe — •Davide Romano — Rome, Italy

I shall present a general strategy for the classical limit problem in the context of the de Broglie-Bohm theory. In this framework, the problem reduces to the following questions: 1. Why does the wave-function disappear in the classical regime? 2. Why do the Bohmian trajectories become (approximately) Newtonian? The answer to the first question is due to the formation of well-localized effective wave-functions for the subsystems of entangled states. This process also provides a physical explanation for decoherence effects of open quantum systems. Concerning the second question, I will suggest a solution that makes use of a combination of decoherence and quantum potential (Q). It is well-known, in fact, that when Q is negligible the Bohmian particles follow a Newtonian trajectory. Problem: Q cannot be made negligible for all the states (Q=constant for a stationary wave, for example). However, the classical regime is necessarily a decoherence regime, and it can be shown (Zurek, Habib and Paz (1993), Coherent states via decoherence, Physical Review Letters) that the emerging wave functions from decoherence will be Gaussian states. This is a good result: in fact, the quantum potential of a Gaussian state is negligible under the conditions of big mass, small de Broglie wave-length and negligible quantum action. These conditions are the hallmark of the classical regime: this finally shows that a macroscopic Bohmian system in interaction with the environment will follow an (approximately) Newtonian trajectory.