8,973 research outputs found
Thermodynamics with generalized ensembles: The class of dual orthodes
We address the problem of the foundation of generalized ensembles in
statistical physics. The approach is based on Boltzmann's concept of orthodes.
These are the statistical ensembles that satisfy the heat theorem, according to
which the heat exchanged divided by the temperature is an exact differential.
This approach can be seen as a mechanical approach alternative to the well
established information-theoretic one based on the maximization of generalized
information entropy. Our starting point are the Tsallis ensembles which have
been previously proved to be orthodes, and have been proved to interpolate
between canonical and microcanonical ensembles. Here we shall see that the
Tsallis ensembles belong to a wider class of orthodes that include the most
diverse types of ensembles. All such ensembles admit both a microcanonical-like
parametrization (via the energy), and a canonical-like one (via the parameter
). For this reason we name them ``dual''. One central result used to
build the theory is a generalized equipartition theorem. The theory is
illustrated with a few examples and the equivalence of all the dual orthodes is
discussed.Comment: 20 pages, 4 figures. Minor improvement
Quantum Fluctuation Relations for Ensembles of Wave Functions
New quantum fluctuation relations are presented. In contrast with the the
standard approach, where the initial state of the driven system is described by
the (micro)canonical density matrix, here we assume that it is described by a
(micro)canonical distribution of wave functions, as originally proposed by
Schr\"odinger. While the standard fluctuation relations are based on von
Neumann measurement postulate, these new fluctuation relations do not involve
any quantum collapse, but involve instead a notion of work as the change in
expectation of the Hamiltonian.Comment: 12 pages, 1 figure. Added illustrative example in v2. Accepted for
publication in New Journal of Physic
Complementary expressions for the entropy-from-work theorem
We establish an expression of the entropy-from-work theorem that is
complementary to the one originally proposed in [P. Talkner, P. Hanggi and M.
Morillo, arXiv:0707.2307]. In the original expression the final energy is fixed
whereas in the present expression the initial energy is fixed.Comment: 2 Page
On the Limiting Cases of Nonextensive Thermostatistics
We investigate the limiting cases of Tsallis statistics. The viewpoint
adopted is not the standard information-theoretic one, where one derives the
distribution from a given measure of information. Instead the mechanical
approach recently proposed in [M. Campisi, G.B. Bagci, Phys. Lett. A (2006),
doi:10.1016/j.physleta.2006.09.081], is adopted, where the distribution is
given and one looks for the associated physical entropy. We show that, not only
the canonical ensemble is recovered in the limit of tending to one, as one
expects, but also the microcanonical ensemble is recovered in the limit of
tending to minus infinity. The physical entropy associated with Tsallis
ensemble recovers the microcanonical entropy as well and we note that the
microcanonical equipartition theorem is recovered too. We are so led to
interpret the extensivity parameter q as a measure of the thermal bath heat
capacity: (i.e. canonical) corresponds to an infinite bath (thermalised
case, temperature is fixed), (microcanonical) corresponds to a bath
with null heat capacity (isolated case, energy is fixed), intermediate
(i.e. Tsallis) correspond to the realistic cases of finite heat capacity (both
temperature and energy fluctuate).Comment: 5 pages, 2 figure
Comment on "Experimental Verification of a Jarzynski-Related Information-Theoretic Equality by a Single Trapped Ion" PRL 120 010601 (2018)
The target paper presents an experimental verification of a
"Jarzynski-related" equality. We show that the latter equality is in fact not
related to the Jarzynski equality.Comment: 1 pag
- …