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Optimal Protocol for Maximum Work Extraction in a Feedback Process with a Time-varying Potential
권철안 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.12
The nonequilibrium nature of information thermodynamics is characterized by the inequality or non-negativity of the total entropy change of the system, memory, and reservoir. Mutual information change plays a crucial role in the inequality, in particular if work is extracted and the paradox of Maxwell’s demon is raised. We consider the Brownian information engine where the protocol set of the harmonic potential is initially chosen by the measurement and varies in time. We confirm the inequality of the total entropy change by calculating, in detail, the entropic terms including the mutual information change. We rigorously find the optimal values of the time-dependent protocol for maximum extraction of work both for the finite-time and the quasi-static process.
Path-dependent Entropy Production
권철안 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.5
A rigorous derivation of nonequilibrium entropy production via the path-integral formalism is presented. Entropy production is defined as the entropy change piled in a heat reservoir as a result of a nonequilibrium thermodynamic process. It is a central quantity by which various forms of the fluctuation theorem are obtained. The two kinds of the stochastic dynamics are investigated: the Langevin dynamics for an even-parity state and the Brownian motion of a single particle. Mathematical ambiguities in deriving the functional form of the entropy production, which depends on path in state space, are clarified by using a rigorous quantum mechanical approach.
Nonequilibrium thermodynamics for a harmonic potential moving in time
Lee Hyun Keun,Kwon Youngchae,권철안 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.83 No.5
We investigate non-equilibrium thermodynamics externally driven by moving the center of harmonic potential in time. We present the theoretical formalism for an arbitrary motion in underdamped dynamics. We provide the formulas to find thermodynamic quantities such as work, heat and entropy production produced for time period, which are main quantities in non-equilibrium studies. For sinusoidal driving with external frequency Ω, we observe a resonance for work production where the average rate for infinite period is maximized at Ω = ω0 that is the internal frequency of the harmonic oscillator. It may be used for an alternative way to measure the stiffness of an optical trap potential. We confirm the thermodynamic uncertainty relation newly found for underdamped dynamics subject to general time-dependent protocols for a specific example of driving.