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1	The Approach to Equilibration in Closed Quantum Systems / Equilibrierung von abgeschlossenen Quantensystemen Niemeyer, Hendrik 03 July 2014 (has links) The question whether and how closed quantum systems equilibrate is still debated today. In this thesis a generic spin system is analysed and criteria to classify unique equilibration dynamics are developed. Furthermore, the eigenstate thermalization hypothesis is investigated as a possible cause for the unique equilibrium. For both problems novel numerical methods for solving the time-dependent Schroedinger equation based on series expansions and typicality are developed. Furthermore, the problem of markovian dynamics on the level of single measurements is discussed. Quantenthermodynamik Quantenmechanik Thermodynamik Heisenbergmodell 33.23 - Quantenphysik ddc:530
2	Phase diagrams of two-dimensional frustrated spin systems / Phasendiagramme für zweidimensionale frustrierte Spinsysteme Kalz, Ansgar 22 March 2012 (has links) No description available. 530 Physik RDI 800 Physics korreliert magnetisch zweidimensional frustriert Spinmodell Phasenübergang Grundzustand Isingmodell Heisenbergmodell Quantenfluktuation Quadratgitter Honeycombgitter correlated magnetic two-dimensional frustrated spin model Ising Heisenberg ground state phase transition quantum fluctuations square lattice honeycomb lattice 33.10 33.23 33.61 33.64