2,395 research outputs found
Thermodynamics of a classical ideal gas at arbitrary temperatures
We propose a fundamental relation for a classical ideal gas that is valid at
all temperatures with remarkable accuracy. All thermodynamical properties of
classical ideal gases can be deduced from this relation at arbitrary
temperature.Comment: 7 pages, Latex, with 2 additional files for pslatex figures.
Expression for entropy added in the 2nd versio
The diocotron instability in a quasi-toroidal geometry
Slipstream instability of low density electron beams in crossed electric and magnetic field
Rheology of Granular Materials: Dynamics in a Stress Landscape
We present a framework for analyzing the rheology of dense driven granular
materials, based on a recent proposal of a stress-based ensemble. In this
ensemble fluctuations in a granular system near jamming are controlled by a
temperature-like parameter, the angoricity, which is conjugate to the stress of
the system. In this paper, we develop a model for slowly driven granular
materials based on the stress ensemble and the idea of a landscape in stress
space. The idea of an activated process driven by the angoricity has been shown
by Behringer et al (2008) to describe the logarithmic strengthening of granular
materials. Just as in the Soft Glassy Rheology (SGR) picture, our model
represents the evolution of a small patch of granular material (a mesoscopic
region) in a stress-based trap landscape. The angoricity plays the role of the
fluctuation temperature in SGR. We determine (a) the constitutive equation, (b)
the yield stress, and (c) the distribution of stress dissipated during granular
shearing experiments, and compare these predictions to experiments of Hartley &
Behringer (2003).Comment: 17 pages, 4 figure
Optimal energy quanta to current conversion
We present a microscopic discussion of a nano-sized structure which uses the
quantization of energy levels and the physics of single charge Coulomb
interaction to achieve an optimal conversion of heat flow to directed current.
In our structure the quantization of energy levels and the Coulomb blockade
lead to the transfer of quantized packets of energy from a hot source into an
electric conductor to which it is capacitively coupled. The fluctuation
generated transfer of a single energy quantum translates into the directed
motion of a single electron. Thus in our structure the ratio of the charge
current to the heat current is determined by the ratio of the charge quantum to
the energy quantum. An important novel aspect of our approach is that the
direction of energy flow and the direction of electron motion are decoupled.Comment: 9 pages, 6 figure
Thermodynamic consistency of liquid-gas lattice Boltzmann simulations
Lattice Boltzmann simulations have been very successful in simulating
liquid-gas and other multi-phase fluid systems. However, the underlying second
order analysis of the equation of motion has long been known to be insufficient
to consistently derive the fourth order terms that are necessary to represent
an extended interface. These same terms are also responsible for thermodynamic
consistency, i.e. to obtain a true equilibrium solution with both a constant
chemical potential and a constant pressure. In this article we present an
equilibrium analysis of non-ideal lattice Boltzmann methods of sufficient order
to identify those higher order terms that lead to a lack of thermodynamic
consistency. We then introduce a thermodynamically consistent forcing method.Comment: 12 pages, 8 figure
Coherence properties of the microcavity polariton condensate
A theoretical model is presented which explains the dominant decoherence
process in a microcavity polariton condensate. The mechanism which is invoked
is the effect of self-phase modulation, whereby interactions transform
polariton number fluctuations into random energy variations. The model shows
that the phase coherence decay, g1(t), has a Kubo form, which can be Gaussian
or exponential, depending on whether the number fluctuations are slow or fast.
This fluctuation rate also determines the decay time of the intensity
correlation function, g2(t), so it can be directly determined experimentally.
The model explains recent experimental measurements of a relatively fast
Gaussian decay for g1(t), but also predicts a regime, further above threshold,
where the decay is much slower.Comment: 5 pages, 1 figur
Measuring thermodynamic length
Thermodynamic length is a metric distance between equilibrium thermodynamic
states. Among other interesting properties, this metric asymptotically bounds
the dissipation induced by a finite time transformation of a thermodynamic
system. It is also connected to the Jensen-Shannon divergence, Fisher
information and Rao's entropy differential metric. Therefore, thermodynamic
length is of central interest in understanding matter out-of-equilibrium. In
this paper, we will consider how to define thermodynamic length for a small
system described by equilibrium statistical mechanics and how to measure
thermodynamic length within a computer simulation. Surprisingly, Bennett's
classic acceptance ratio method for measuring free energy differences also
measures thermodynamic length.Comment: 4 pages; Typos correcte
Mean-field calculation of critical parameters and log-periodic characterization of an aperiodic-modulated model
We employ a mean-field approximation to study the Ising model with aperiodic
modulation of its interactions in one spatial direction. Two different values
for the exchange constant, and , are present, according to the
Fibonacci sequence. We calculated the pseudo-critical temperatures for finite
systems and extrapolate them to the thermodynamic limit. We explicitly obtain
the exponents , , and and, from the usual scaling
relations for anisotropic models at the upper critical dimension (assumed to be
4 for the model we treat), we calculate , , , ,
and . Within the framework of a renormalization-group approach, the
Fibonacci sequence is a marginal one and we obtain exponents which depend on
the ratio , as expected. But the scaling relation is obeyed for all values of we studied. We characterize
some thermodynamic functions as log-periodic functions of their arguments, as
expected for aperiodic-modulated models, and obtain precise values for the
exponents from this characterization.Comment: 17 pages, including 9 figures, to appear in Phys. Rev.
Generalized Phase Rules
For a multi-component system, general formulas are derived for the dimension
of a coexisting region in the phase diagram in various state spaces.Comment: In the revised manuscript, physical meanings of D's are explained by
adding three figures. 10 pages, 3 figure
Equilibrium and nonequilibrium thermodynamics of particle-stabilized thin liquid films
Our recent quasi-two-dimensional thermodynamic description of thin-liquid
films stabilized by colloidal particles is generalized to describe nonuniform
equilibrium states of films in external potentials and nonequilibrium transport
processes produced in the film by gradients of thermodynamic forces. Using a
Monte--Carlo simulation method, we have determined equilibrium equations of
state for a film stabilized by a suspension of hard spheres. Employing a
multipolar-expansion method combined with a flow-reflection technique, we have
also evaluated the short-time film-viscosity coefficients and collective
particle mobility.Comment: 16 pages, 10 figure
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