975 research outputs found
Thermodynamic Irreversibility from high-dimensional Hamiltonian Chaos
This paper discusses the thermodynamic irreversibility realized in
high-dimensional Hamiltonian systems with a time-dependent parameter. A new
quantity, the irreversible information loss, is defined from the Lyapunov
analysis so as to characterize the thermodynamic irreversibility. It is proved
that this new quantity satisfies an inequality associated with the second law
of thermodynamics. Based on the assumption that these systems possess the
mixing property and certain large deviation properties in the thermodynamic
limit, it is argued reasonably that the most probable value of the irreversible
information loss is equal to the change of the Boltzmann entropy in statistical
mechanics, and that it is always a non-negative value. The consistency of our
argument is confirmed by numerical experiments with the aid of the definition
of a quantity we refer to as the excess information loss.Comment: LaTeX 43 pages (using ptptex macros) with 11 figure
Non-ergodic transitions in many-body Langevin systems: a method of dynamical system reduction
We study a non-ergodic transition in a many-body Langevin system. We first
derive an equation for the two-point time correlation function of density
fluctuations, ignoring the contributions of the third- and fourth-order
cumulants. For this equation, with the average density fixed, we find that
there is a critical temperature at which the qualitative nature of the
trajectories around the trivial solution changes. Using a method of dynamical
system reduction around the critical temperature, we simplify the equation for
the time correlation function into a two-dimensional ordinary differential
equation. Analyzing this differential equation, we demonstrate that a
non-ergodic transition occurs at some temperature slightly higher than the
critical temperature.Comment: 8 pages, 1 figure; ver.3: Calculation errors have been fixe
The law of action and reaction for the effective force in a nonequilibrium colloidal system
We study a nonequilibrium Langevin many-body system containing two 'test'
particles and many 'background' particles. The test particles are spatially
confined by a harmonic potential, and the background particles are driven by an
external driving force. Employing numerical simulations of the model, we
formulate an effective description of the two test particles in a
nonequilibrium steady state. In particular, we investigate several different
definitions of the effective force acting between the test particles. We find
that the law of action and reaction does not hold for the total mechanical
force exerted by the background particles, but that it does hold for the
thermodynamic force defined operationally on the basis of an idea used to
extend the first law of thermodynamics to nonequilibrium steady states.Comment: 13 page
Effects of Littlest Higgs model in rare D meson decays
A tree-level flavor changing neutral current in the up-like quark sector
appears in one of the variations of the Littlest Higgs model. We investigate
the effects of this coupling in the D+ -> pi+ l+ l- and D0 -> rho0 l+ l-
decays, which are the most appropriate candidates for the experimental studies.
However, the effects are found to be too small to be observed in the current
and the foreseen experimental facilities. These decays are still dominated by
the standard model long-distance contributions, which are reevaluated based on
the new experimental input.Comment: 13 pages, 3 figures; new constraint on scale f taken into account and
effects on charm meson decays recalculate
An order parameter equation for the dynamic yield stress in dense colloidal suspensions
We study the dynamic yield stress in dense colloidal suspensions by analyzing
the time evolution of the pair distribution function for colloidal particles
interacting through a Lennard-Jones potential. We find that the equilibrium
pair distribution function is unstable with respect to a certain anisotropic
perturbation in the regime of low temperature and high density. By applying a
bifurcation analysis to a system near the critical state at which the stability
changes, we derive an amplitude equation for the critical mode. This equation
is analogous to order parameter equations used to describe phase transitions.
It is found that this amplitude equation describes the appearance of the
dynamic yield stress, and it gives a value of 2/3 for the shear thinning
exponent. This value is related to the mean field value of the critical
exponent in the Ising model.Comment: 8 pages, 2 figure
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