Theoretical Study on the Foundation of Statistical Mechanics in Isolated Quantum Systems
達彦 池田
氏名 池田 達彦The main theme of this thesis is the foundation of statistical mechanics in isolated quantum systems: how equilibrium states, or macroscopically unchanging states, emerge in the course of the unitary time evolution, why they are well described by the microcanonical ensemble, and how the thermodynamic entropy is interpreted from a quantum-mechanical viewpoint.Isolated quantum systems are by definition not in contact with a heat bath and, thus, they never lose their memory of the initial state to reach thermal equilibrium by throwing away the information to the bath.Therefore, to address the questions raised above, we must find out the inherent ability of isolated quantum systems to undergo thermalization.The foundation has been studied since the early 20th century because an isolated system plays the most fundamental role in statistical mechanics.Presupposing that the microcanonical ensemble describes thermal equilibrium states in isolated systems, the canonical ensemble, for example, is deduced in systems in contact with a heat bath.Despite its importance, the foundation is still only presupposed and has not been fully proven yet.Recently, the theme has attracted renewed attention because isolated quantum systems have experimentally been realized using ultracold atoms, which are trapped by lasers in a high vacuum.Until then, it had been of purely theoretical interest, and thermalization of most quantum systems in reality had often been ascribed to the coupling with their environment.Now that thermalization is actually observed in ultracold atom experiments, the theme is of interest not only theoretically but also experimentally.
•Mar 24, 2015•2 citations