95 research outputs found
Thermodynamic Entropy And The Accessible States of Some Simple Systems
Comparison of the thermodynamic entropy with Boltzmann's principle shows that
under conditions of constant volume the total number of arrangements in simple
thermodynamic systems with temperature-independent heat capacities is TC/k. A
physical interpretation of this function is given for three such systems; an
ideal monatomic gas, an ideal gas of diatomic molecules with rotational motion,
and a solid in the Dulong-Petit limit of high temperature. T1/2 emerges as a
natural measure of the number of accessible states for a single particle in one
dimension. Extension to N particles in three dimensions leads to TC/k as the
total number of possible arrangements or microstates. The different microstates
of the system are thus shown a posteriori to be equally probable, with
probability T-C/k, which implies that for the purposes of counting states the
particles of the gas are distinguishable. The most probable energy state of the
system is determined by the degeneracy of the microstates.Comment: 9 pages, 1 figur
Ehrenfest's scheme and thermodynamic geometry in Born-Infeld AdS black holes
In this paper we analyze the phase transition phenomena in Born-Infeld AdS
black holes using Ehrenfest's scheme of standard thermodynamics. The critical
points are marked by the divergences in the heat capacity. In order to
investigate the nature of the phase transition, we analytically check both the
Ehrenfest's equations near the critical points. Our analysis reveals that this
is indeed a second order phase transition. Finally, we analyze the nature of
the phase transition using state space geometry approach. This is found to be
compatible with the Ehrenfest's scheme.Comment: Published versio
Critical behavior of Born Infeld AdS black holes in higher dimensions
Based on a canonical framework, we investigate the critical behavior of
Born-Infeld AdS black holes in higher dimensions. As a special case,
considering the appropriate limit, we also analyze the critical phenomena for
Reissner Nordstrom AdS black holes. The critical points are marked by the
divergences in the heat capacity at constant charge. The static critical
exponents associated with various thermodynamic entities are computed and shown
to satisfy the thermodynamic scaling laws. These scaling laws have also been
found to be compatible with the static scaling hypothesis. Furthermore, we show
that the values of these exponents are universal and do not depend on the
spatial dimensionality of the AdS space. We also provide a suggestive way to
calculate the critical exponents associated with the spatial correlation which
satisfy the scaling laws of second kind.Comment: LaTex, 22 pages, 12 figures, minor modifications in text, To appear
in Phys. Rev.
Effective thermodynamics of strongly coupled qubits
Interactions between a quantum system and its environment at low temperatures
can lead to violations of thermal laws for the system. The source of these
violations is the entanglement between system and environment, which prevents
the system from entering into a thermal state. On the other hand, for two-state
systems, we show that one can define an effective temperature, placing the
system into a `pseudo-thermal' state where effective thermal laws are upheld.
We then numerically explore these assertions for an n-state system inspired by
the spin-boson environment.Comment: 9 pages, 3 figure
Simulational nanoengineering: Molecular dynamics implementation of an atomistic Stirling engine
A nanoscale-sized Stirling engine with an atomistic working fluid has been
modeled using molecular dynamics simulation. The design includes heat
exchangers based on thermostats, pistons attached to a flywheel under load, and
a regenerator. Key aspects of the behavior, including the time-dependent flows,
are described. The model is shown to be capable of stable operation while
producing net work at a moderate level of efficiency.Comment: 4 pages, 8 figures (minor changes
Effective Action and Thermodynamics of Radiating Shells in General Relativity
An effective action is obtained for the area and mass aspect of a thin shell
of radiating self-gravitating matter. On following a mini-superspace approach,
the geometry of the embedding space-time is not dynamical but fixed to be
either Minkowski or Schwarzschild inside the shell and Vaidya in the external
space filled with radiation. The Euler-Lagrange equations of motion are
discussed and shown to entail the expected invariance of the effective
Lagrangian under time-reparametrization. They are equivalent to the usual
junction equations and suggest a macroscopic quasi-static thermodynamic
description.Comment: LATeX, 20 pages, 2 Fig
Carnot cycle for an oscillator
Carnot established in 1824 that the efficiency of cyclic engines operating
between a hot bath at absolute temperature and a bath at a lower
temperature cannot exceed . We show that linear
oscillators alternately in contact with hot and cold baths obey this principle
in the quantum as well as in the classical regime. The expression of the work
performed is derived from a simple prescription. Reversible and non-reversible
cycles are illustrated. The paper begins with historical considerations and is
essentially self-contained.Comment: 19 pages, 3 figures, sumitted to European Journal of Physics Changed
content: Fluctuations are considere
Ideal gas sources for the Lemaitre-Tolman-Bondi metrics
New exact solutions emerge by replacing the dust source of the
Lem\^aitre-Tolman-Bondi metrics with a viscous fluid satisfying the monatomic
gas equation of state. The solutions have a consistent thermodynamical
interpretation. The most general transport equation of Extended Irreversible
Thermodynamics is satisfied, with phenomenological coefficients bearing a close
resemblance to those characterizing a non relativistic Maxwell-Bolzmann gas.Comment: 7 pages, Plain TeX with IOP macros, important corrections to previous
version, 3 figures (to appear in Classical and Quantum Gravity, June 1998
Temperature dependence of bulk viscosity in water using acoustic spectroscopy
Despite its fundamental role in the dynamics of compressible fluids, bulk
viscosity has received little experimental attention and there remains a
paucity of measured data. Acoustic spectroscopy provides a robust and accurate
approach to measuring this parameter. Working from the Navier-Stokes model of a
compressible fluid one can show that the bulk viscosity makes a significant and
measurable contribution to the frequency-squared acoustic attenuation. Here we
employ this methodology to determine the bulk viscosity of Millipore water over
a temperature range of 7 to 50 degrees Celsius. The measured attenuation
spectra are consistent with the theoretical predictions, while the bulk
viscosity of water is found to be approximately three times larger than its
shear counterpart, reinforcing its significance in acoustic propagation.
Moreover, our results demonstrate that this technique can be readily and
generally applied to fluids to accurately determine their temperature dependent
bulk viscosities.Comment: 7 pages, 4 figures. Proceedings of the Anglo-French Physical
Acoustics Conference, January 201
Universal restrictions to the conversion of heat into work derived from the analysis of the Nernst theorem as a uniform limit
We revisit the relationship between the Nernst theorem and the Kelvin-Planck
statement of the second law. We propose that the exchange of entropy uniformly
vanishes as the temperature goes to zero. The analysis of this assumption shows
that is equivalent to the fact that the compensation of a Carnot engine scales
with the absorbed heat so that the Nernst theorem should be embedded in the
statement of the second law.
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Se analiza la relaci{\'o}n entre el teorema de Nernst y el enunciado de
Kelvin-Planck del segundo principio de la termodin{\'a}mica. Se{\~n}alamos el
hecho de que el cambio de entrop{\'\i}a tiende uniformemente a cero cuando la
temperatura tiende a cero. El an{\'a}lisis de esta hip{\'o}tesis muestra que es
equivalente al hecho de que la compensaci{\'o}n de una m{\'a}quina de Carnot
escala con el calor absorbido del foco caliente, de forma que el teorema de
Nernst puede derivarse del enunciado del segundo principio.Comment: 8pp, 4 ff. Original in english. Also available translation into
spanish. Twocolumn format. RevTe
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