12,127 research outputs found
An expression for stationary distribution in nonequilibrium steady state
We study the nonequilibrium steady state realized in a general stochastic
system attached to multiple heat baths and/or driven by an external force.
Starting from the detailed fluctuation theorem we derive concise and suggestive
expressions for the corresponding stationary distribution which are correct up
to the second order in thermodynamic forces. The probability of a microstate
is proportional to where
is the excess entropy change.
Here is the difference between two kinds of conditioned
path ensemble averages of excess heat transfer from the -th heat bath whose
inverse temperature is . Our expression may be verified experimentally
in nonequilibrium states realized, for example, in mesoscopic systems.Comment: 4 pages, 2 figure
Properties of Color-Coulomb String Tension
We study the properties of the color-Coulomb string tension obtained from the
instantaneous part of gluon propagators in Coulomb gauge using quenched SU(3)
lattice simulation.
In the confinement phase, the dependence of the color-Coulomb string tension
on the QCD coupling constant is smaller than that of the Wilson loop string
tension. On the other hand, in the deconfinement phase, the color-Coulomb
string tension does not vanish even for , the temperature
dependence of which is comparable with the magnetic scaling, dominating the
high temperature QCD. Thus, the color-Coulomb string tension is not an order
parameter of QGP phase transition.Comment: 17 pages, 5 figures; one new figure added, typos corrected, version
to appear in PR
Roundabout relaxation: collective excitation requires a detour to equilibrium
Relaxation to equilibrium after strong and collective excitation is studied,
by using a Hamiltonian dynamical system of one dimensional XY model. After an
excitation of a domain of elements, the excitation is concentrated to fewer
elements, which are made farther away from equilibrium, and the excitation
intensity increases logarithmically with . Equilibrium is reached only after
taking this ``roundabout'' route, with the time for relaxation diverging
asymptotically as with .Comment: 4 pages, 5 figure
The S shape of a granular pile in a rotating drum
The shape of a granular pile in a rotating drum is investigated. Using
Discrete Elements Method (DEM) simulations we show that the "S shape" obtained
for high rotation speed can be accounted for by the friction on the end plates.
A theoretical model which accounts for the effect of the end plates is
presented and the equation of the shape of the free surface is derived. The
model reveals a dimensionless number which quantifies the influence of the end
plates on the shape of the pile. Finally, the scaling laws of the system are
discussed and numerical results support our conclusions
Dust Size Growth and Settling in a Protoplanetary Disk
We have studied dust evolution in a quiescent or turbulent protoplanetary
disk by numerically solving coagulation equation for settling dust particles,
using the minimum mass solar nebular model. As a result, if we assume an
ideally quiescent disk, the dust particles settle toward the disk midplane to
form a gravitationally unstable layer within 2x10^3 - 4x10^4 yr at 1 - 30 AU,
which is in good agreement with an analytic calculation by Nakagawa, Sekiya, &
Hayashi (1986) although they did not take into account the particle size
distribution explicitly. In an opposite extreme case of a globally turbulent
disk, on the other hand, the dust particles fluctuate owing to turbulent motion
of the gas and most particles become large enough to move inward very rapidly
within 70 - 3x10^4 yr at 1 - 30 AU, depending on the strength of turbulence.
Our result suggests that global turbulent motion should cease for the
planetesimal formation in protoplanetary disks.Comment: 27 pages, 8 figures, accepted for publication in the Ap
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