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Work and heat at the mesoscale
Pajger, Šimon ; Ryabov, Artem (advisor) ; Kolář, Michal (referee)
Title: Work and heat at the mesoscale Author: Bc. Šimon Pajger Department: Department of Macromolecular Physics Supervisor: RNDr. Artem Ryabov, Ph.D., KMF MFF UK Abstract: Understanding the conversion between heat and work by heat engines led to the discoveries of entropy and to the formulation of the Second law of clas- sical macroscopic thermodynamics. At the microscale and mesoscale, quantum coherences are a potential resource for various quantum processes. Quantum coherences can be used to enhance the performance of various devices beyond the limits demanded by classical physics. Recently many models have been es- tablished clarifying how coherences affect the speed and irreversibility of ther- modynamic processes and raising the question of what experimentally relevant consequences various generalizations of the formalism of classical thermodynam- ics to the microscopic level may have. Here we study a few of these models in great detail. Specifically, we discuss fluctuations of coherence-enhanced heat currents, propose a model of a heat engine that does work while being in a steady state, and derive a condition on the rate of decoherence that specifies, when coherence-enhanced currents provide a significant advantage over the case without any coherence. Then we discuss coherence-inducing heat bath...
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Entropy production and irreversibility in transition state theory
Pajger, Šimon ; Ryabov, Artem (advisor) ; Novotný, Tomáš (referee)
Title: Entropy production and irreversibility in transition state theory Author: Šimon Pajger Department: Department of Macromolecular Physics Supervisor: RNDr. Artem Ryabov, Ph.D., Department of Macromolecular Physics Abstract: Modern experiments focusing on durations of nonequilibrium transi- tions provide valuable information on the underlying microscopic kinetics. Theo- retically, outcomes of such experiments are well understood for time-independent free energy landscapes only. Amongst the most fundamental results in this area belongs an identity of distributions of times of forward and backward transitions between arbitrary two points of a free energy landscape. However, recently it has been experimentally found, that this identity can be broken by an action of external time-dependent force. In the thesis, we explore this situation theo- retically and discuss under which conditions the identity of distributions can be restored. To this end, we introduce distributions of transition times weighted by the entropy production. In particular, we show that it is possible to find weight for each trajectory, such that weighted distributions of transition times resulting from such weights are identical. Assuming an external harmonic time-dependent force, we discuss two experimentally relevant situations. First,...
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