3,114 research outputs found
Gibbs Entropy and Irreversibility
This contribution is dedicated to dilucidating the role of the Gibbs entropy
in the discussion of the emergence of irreversibility in the macroscopic world
from the microscopic level. By using an extension of the Onsager theory to the
phase space we obtain a generalization of the Liouville equation describing the
evolution of the distribution vector in the form of a master equation. This
formalism leads in a natural way to the breaking of the BBGKY hierarchy. As a
particular case we derive the Boltzmann equation
The non-equilibrium work relation. Thermodynamic analysis and microscopic foundations
We discuss the conditions for which the non-equilibrium work relation is
valid by means of thermodynamic and microscopic arguments.Comment: 16 pages 1 figur
Quantum Theory of Irreversibility
A generalization of the Gibbs-von Neumann relative entropy is proposed based
on the quantum BBGKY [Bogolyubov-Born-Green-Kirkwood-Yvon] hierarchy as the
nonequilibrium entropy for an N-body system. By using a generalization of the
Liouville-von Neumann equation describing the evolution of a density super-
operator, it is demonstrated that the entropy production for an isolated system
is non-negative, which provides an arrow of time. Moreover, following the
procedure of non-equilibrium thermodynamics a master matrix is introduced for
which a mi- croscopic expression is obtained. Then, the quantum Boltzmann
equation is derived in terms of a transition superoperator related to that
master matrix
Llibertat, igualtat i laĂŻcitat en lâĂ mbit educatiu
Els atemptats de lâ11-S de 2001 als Estats Units, a Bali el 2002, a Madrid el 2003, i a Londres el 2005 âentre dâaltres factorsâ han provocat que la religiĂł estigui mĂ©s present a les agendes polĂtiques, socials i culturals dels paĂŻsos dâarreu del mĂłn, malgrat les declaracions reiterades que rebutgen una identificaciĂł a priori entre terrorisme i religiĂł. ReligiĂł i seguretat conformen, doncs, un nou binomi, un nou enfocament per a la promociĂł dels drets humans i per a la prevenciĂł de la pau internacional. I lâensenyament nâha de ser una de les peces clau
Mesoscopic non-equilibrium thermodynamics approach to the dynamics of polymers
We present a general formalism able to derive the kinetic equations of
polymer dynamics. It is based on the application of nonequilibrium
thermodynamics to analyze the irreversible processes taking place in the
conformational space of the macromolecules. The Smoluchowski equation results
from the analysis of the underlying diffusion process in that space within the
scheme of nonequilibrium thermodynamics. We apply the method to different
situations, concerning flexible, semiflexible and rod-like polymers and to the
case of more concentrated solutions in which interactions become important.Comment: 13 pages (RevTex). To be published in Physica
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