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Quantum Limits to the Second Law of Thermodynamics |
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New Challenges to the Second Law First Conference |
Allahverdyan Armen E., Roger Balian, Theo M. Nieuwenhuizen Thomson`s formulation of the second law - no work can be extracted from a system coupled to a bath through a cyclic process - is believed to be a fundamental principle of nature. For the equilibrium situation a simple proof is presented, valid for macroscopic sources of work. Thomson`s formulation gets limited when the source of work is mesoscopic, i.e. when its number of degrees of freedom is large but finite. Here work-extraction from a single equilibrium thermal bath is possible when its temperature is large enough. This result is illustrated by means of exactly solvable models. Finally we consider the Clausius principle: heat goes from high to low temperature. A theorem and some simple consequences for this statement are pointed out.
Crosignani Bruno, Paolo Di Porto, and Claudio Conti Denur Jack Duncan Todd L. Claims of exceptions to the second law of thermodynamics are
generally met with extreme skepticism that is quite reasonable
given the great confidence placed in the second law. But what
specifically is the basis for that confidence? The perspective
from which we approach experimental or theoretical results that
call into question the absolute status of the second law depends
greatly on our understanding of why it must be true. For example,
a belief that there are solid theoretical arguments demonstrating
that the second law must be true leads to a very different
perspective than a belief that the law is simply a generalization
of empirical observations. This paper will briefly survey and
examine some of the basic arguments on which our confidence in
the second law might be based, to help provide a well-informed
perspective for evaluating the various claims presented at this
conference.
http://xxx.lanl.gov/abs/cond-mat/0208291 Nieuwenhuizen Theo M. , Armen E. Allahverdyan The Brownian motion of a harmonically bound quantum particle and coupled to a harmonic quantum bath is exactly solvable. At low enough temperatures the stationary state is non-Gibbsian due to an entanglement with the bath. This happens when a cloud of bath modes around the particle is formed. Equilibrium thermodynamics for particle plus bath together, does not imply standard thermodynamics for the particle itself at low T. Various formulations of the second law are then invalid. First, the Clausius inequality can be violated. Second, when the width of the confining potential is suddenly changed, there occurs a relaxation to equilibrium during which the rate of entropy production is partly negative. Third, for non-adiabatic changes of system parameters the rate of energy dissipation can be negative, and, out of equilibrium, cyclic processes are possible which extract work from the bath. Conditions are put forward under which perpetuum mobile of the second kind, having several work extraction cycles, enter the realm of condensed matter physics.
Pombo Claudia, Armen E. Allahverdyan, Theo M. Nieuwenhuizen The spin-boson model, often used in NMR and ESR physics, quantum optics and spintronics, is considered in a solvable limit to model a spin one-half particle interacting with a bosonic thermal bath. By applying external pulses to a non-equilibrium initial state of the spin, work can be extracted from the thermalized bath. It occurs on the timescale T_2 inherent to transversal (`quantum`) fluctuations. The work (partly) arises from heat given off by the surrounding bath, while the spin entropy remains constant during a pulse. This presents a violation of the Clausius inequality and the Thomson formulation of the second law (cycles cost work) for the two-level system.
Raji Heyrovska |
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Preface
Chernogolovka, IMT RAS
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