Spelling suggestions: "subject:"33.25 thermodynamik"" "subject:"33.25 termodynamik""
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Friction and diffusive light transport in a granular medium / Reibung und diffusiver Lichttransport in granularem StoffUtermann, Sonia 27 January 2012 (has links)
No description available.
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The Approach to Equilibration in Closed Quantum Systems / Equilibrierung von abgeschlossenen QuantensystemenNiemeyer, 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.
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Investigation of the emergence of thermodynamic behavior in closed quantum systems and its relation to standard stochastic descriptionsSchmidtke, Daniel 20 August 2018 (has links)
Our everyday experiences teach us that any imbalance like temperature gradients, non-uniform particle-densities etc. will approach some equilibrium state if not subjected to any external force. Phenomenological descriptions of these empirical findings reach back to the 19th century where Fourier and Fick presented descriptions of relaxation for macroscopic systems by stochastic approaches. However, one of the main goals of thermodynamics remained the derivation of these phenomenological description from basic microscopic principles. This task has gained much attraction since the foundation of quantum mechanics about 100 years ago. However, up to now no such conclusive derivation is presented. In this dissertation we will investigate whether closed quantum systems may show equilibration, and if so, to what extend such dynamics are in accordance with standard thermodynamic behavior as described by stochastic approaches. To this end we consider i.a. Markovian dynamics, Fokker-Planck and diffusion equations. Furthermore, we consider fluctuation theorems as given e.g. by the Jarzynski relation beyond strict Gibbsian initial states. After all we find indeed good agreement for selected quantum systems.
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Aspects of Non-Equilibrium Behavior in Isolated Quantum SystemsHeveling, Robin 06 September 2022 (has links)
Based on the publications [P1–P6], the cumulative dissertation at hand addresses quite diverse
aspects of non-equilibrium behavior in isolated quantum systems. The works presented in
publications [P1, P2] concern the issue of finding generally valid upper bounds on equilibration
times, which ensure the eventual occurrence of equilibration in isolated quantum systems. Recently,
a particularly compelling bound for physically relevant observables has been proposed. Said
bound is examined analytically as well as numerically. It is found that the bound fails to give
meaningful results in a number of standard physical scenarios. Continuing, publication [P4]
examines a particular integral fluctuation theorem (IFT) for the total entropy production of a
small system coupled to a substantially larger but finite bath. While said IFT is known to hold
for canonical states, it is shown to be valid for microcanonical and even pure energy eigenstates
as well by invoking the physically natural conditions of “stiffness” and “smoothness” of transition
probabilities. The validity of the IFT and the existence of stiffness and smoothness are numerically
investigated for various lattice models. Furthermore, this dissertation puts emphasis on the issue
of the route to equilibrium, i.e., to explain the omnipresence of certain relaxation dynamics in
nature, while other, more exotic relaxation patterns are practically never observed, even though
they are a priori not disfavored by the microscopic laws of motion. Regarding this question, the
existence of stability in a larger class of dynamics consisting of exponentially damped oscillations
is corroborated in publication [P6]. In the same vein, existing theories on the ubiquity of certain
dynamics are numerically scrutinized in publication [P3]. Finally, in publication [P5], the recently
proposed “universal operator growth hypothesis”, which characterizes the complexity growth of
operators during unitary time evolution, is numerically probed for various spin-based systems in
the thermodynamic limit. The hypothesis is found to be valid within the limits of the numerical
approach.
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Low Temperature Phase of the m-component Spin Glass / Die Tieftemperaturphase des m-Komponenten SpinglasesBraun, Axel 29 June 2011 (has links)
No description available.
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