Macroscopic Limit of Quantum Systems
Abstract
Classical physics is approached from quantum mechanics in the macroscopic limit. The technical device to achieve this goal is the quantum version of the central limit theorem, derived for an observable at a given time and for the timedependent expectation value of the coordinate. The emergence of the classical trajectory can be followed for the average of an observable over a large set of independent microscopical systems, and the deterministic classical laws can be recovered in all practical purposes, owing to the largeness of Avogadro's number. This result refers to the observed system without considering the measuring apparatus. The emergence of a classical trajectory is followed qualitatively in Wilson's cloud chamber.
 Publication:

Universe
 Pub Date:
 August 2021
 DOI:
 10.3390/universe7090315
 arXiv:
 arXiv:2107.13594
 Bibcode:
 2021Univ....7..315P
 Keywords:

 Quantum Physics;
 Condensed Matter  Statistical Mechanics
 EPrint:
 35 pages, final version to appear in Universe