555 research outputs found
Equilibrium Free Energies from Nonequilibrium Processes
A recent result, relating the (irreversible) work performed on a system
during a non-quasistatic process, to the Helmholtz free energy difference
between two equilibrium states of the system, is discussed. A proof of this
result is given for the special case when the evolution of the system in
question is modelled by a Langevin equation in configuration space.Comment: Conference talk in Zakopane, Poland; 11 pages + 3 figure
Dissipation and lag in irreversible processes
When a system is perturbed by the variation of external parameters, a lag
generally develops between the actual state of the system and the equilibrium
state corresponding to the current parameter values. We establish a
microscopic, quantitative relation between this lag and the dissipated work
that accompanies the process. We illustrate this relation using a model system.Comment: 6 pages, 3 figures, accepted for publication in EP
A quantum version of free energy - irreversible work relations
We give a quantum version of the Jarzynski relation between the distribution
of work done over a certain time-interval on a system and the difference of
equilibrium free energies. The main new ingredient is the identification of
work depending on the quantum history of the system and the proper definition
of various quantum ensembles over which the averages should be made. We also
discuss a number of different regimes that have been considered by other
authors and which are unified in the present set-up. In all cases, and quantum
or classical, it is a general relation between heat and time-reversal that
makes the Jarzynski relation so universally valid
A "fast growth" method of computing free energy differences
Let Delta F be the free energy difference between two equilibrium states of a
system. An established method of numerically computing Delta F involves a
single, long ``switching simulation'', during which the system is driven
reversibly from one state to the other (slow growth, or adiabatic switching).
Here we study a method of obtaining the same result from numerous independent,
irreversible simulations of much shorter duration (fast growth). We illustrate
the fast growth method, computing the excess chemical potential of a
Lennard-Jones fluid as a test case, and we examine the performance of fast
growth as a practical computational tool.Comment: 17 pages + 4 figures, accepted for publication in J.Chem.Phy
Comment on: Failure of the Work-Hamiltonian Connection for Free-Energy Calculations [Phys Rev Lett 100, 020601 (2008), arXiv:0704.0761]
We comment on a Letter by Vilar and Rubi [arXiv:0704.0761].Comment: one page, including one figure; to appear in Phys Rev Let
Fluctuation Theorem in Rachet System
Fluctuation Theorem(FT) has been studied as far from equilibrium theorem,
which relates the symmetry of entropy production. To investigate the
application of this theorem, especially to biological physics, we consider the
FT for tilted rachet system. Under, natural assumption, FT for steady state is
derived.Comment: 6 pages, 2 figure
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