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Related Concept Videos

Entropy Change in Reversible Processes01:10

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In the Carnot engine, which achieves the maximum efficiency between two reservoirs of fixed temperatures, the total change in entropy is zero. The observation can be generalized by considering any reversible cyclic process consisting of many Carnot cycles. Thus, it can be stated that the total entropy change of any ideal reversible cycle is zero.
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In the quest to identify a property that may reliably predict the spontaneity of a process, a promising candidate has been identified: entropy. Scientists refer to the measure of randomness or disorder within a system as entropy. High entropy means high disorder and low energy. To better understand entropy, think of a student’s bedroom. If no energy or work were put into it, the room would quickly become messy. It would exist in a very disordered state, one of high entropy. Energy must be...
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Salt particles that have dissolved in water never spontaneously come back together in solution to reform solid particles. Moreover, a gas that has expanded in a vacuum remains dispersed and never spontaneously reassembles. The unidirectional nature of these phenomena is the result of a thermodynamic state function called entropy (S). Entropy is the measure of the extent to which the energy is dispersed throughout a system, or in other words, it is proportional to the degree of disorder of a...
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The first law of thermodynamics is quantitatively formulated via an equation relating the internal energy of a system, the heat exchanged by it, and the work done on it. A quantitative formulation of the second law of thermodynamics leads to defining a state function, the entropy.
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In the quest to identify a property that may reliably predict the spontaneity of a process, a promising candidate has been identified: entropy. Processes that involve an increase in entropy of the system (ΔS > 0) are very often spontaneous; however, examples to the contrary are plentiful. By expanding consideration of entropy changes to include the surroundings, a significant conclusion regarding the relation between this property and spontaneity may be reached. In thermodynamic models, the...
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Entropy production and non-Markovian dynamical maps.

S Marcantoni1,2, S Alipour3, F Benatti4,5

  • 1Department of Physics, University of Trieste, I-34151, Trieste, Italy.

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|October 1, 2017
PubMed
Summary
This summary is machine-generated.

The second law of thermodynamics may fail for open quantum systems when the environment is ignored. Consistent thermodynamic formulations require explicitly accounting for environmental entropy contributions.

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Area of Science:

  • Quantum Thermodynamics
  • Open Quantum Systems
  • Statistical Mechanics

Background:

  • The weak-coupling limit approach to open quantum systems eliminates the bath, using a master equation for system dynamics.
  • This approach neglects bath entropy contributions to the entropy balance.

Purpose of the Study:

  • To investigate the validity of the second law of thermodynamics in open quantum systems under specific conditions.
  • To analyze entropy production in non-Markovian quantum dynamics.

Main Methods:

  • Analysis of completely positive and trace-preserving, non-Markovian dynamical maps.
  • Examination of systems without the semigroup property.

Main Results:

  • Entropy production can be negative for certain non-Markovian dynamical maps when the bath is ignored.
  • Thermal asymptotic states may not be stationary, leading to negative integrated entropy production.

Conclusions:

  • Relaxing semigroup assumptions in open quantum systems necessitates explicit inclusion of environmental entropy.
  • Consistent thermodynamic formulations require accounting for the environment's contribution to entropy balance.