Biomedical subjects

AE Allahverdyan

Publications and source records attributed to AE Allahverdyan.

3 recordsLinked to original sources

PubMed2000

Extraction of work from a single thermal bath in the quantum regime

The stationary state of a quantum particle strongly coupled to a quantum thermal bath is known to be non-Gibbsian, due to entanglement with the bath. For harmonic potentials, where the system can be described by effective temperatures, thermodynamic relations are shown to take a generalized Gibbsian form that may violate the Clausius inequality. For the weakly anharmonic case, a Fokker-Planck-type description is constructed. It is shown that then work can be extracted from the bath by cyclic variation of a parameter. These apparent violations of the second law are the consequence of quantum coherence in the presence of the slightly off-equilibrium nature of the bath.

Journal Article↗

PubMed2000

Optimizing the classical heat engine

A pair of systems at different temperatures is a classic environment for a heat engine, which produces work during the relaxation to a common equilibrium. It is generally believed that a direct interaction between the two systems will always decrease the amount of the obtainable work, due to inevitable dissipation. Here a situation is reported where, in some time window, work can be gained due to the direct coupling, while dissipation is relevant only for much larger times. Thus, the amount of extracted work increases, at the cost of a change of the final state.

Journal Article↗

PubMed2000

Steady adiabatic state: its thermodynamics, entropy production, energy dissipation, and violation of onsager relations

A class of statistical systems is considered where different degrees of freedom have well-separated characteristic times, and are described by different temperatures. The stationary state is a nonequilibrium state with a heat flow. A generalized statistical thermodynamics is constructed and a universal variational principle is proposed. Entropy production and energy dissipation occur at a constant rate. To leading order in the small ratio of the characteristic times, there exists a universal relation between them. Onsager relations in the context of heat transfer are also considered. They are always broken, except close to equilibrium.

Journal Article↗