296 research outputs found
Dynamical phase transition of a 1D transport process including death
Motivated by biological aspects related to fungus growth, we consider the
competition of growth and corrosion. We study a modification of the totally
asymmetric exclusion process, including the probabilities of injection
and death of the last particle . The system presents a phase transition
at , where the average position of the last particle
grows as . For , a non equilibrium stationary state
exists while for the asymptotic state presents a low density
and max current phases. We discuss the scaling of the density and current
profiles for parallel and sequential updates.Comment: 4 pages, 5 figure
Description of hard sphere crystals and crystal-fluid interfaces: a critical comparison between density functional approaches and a phase field crystal model
In materials science the phase field crystal approach has become popular to
model crystallization processes. Phase field crystal models are in essence
Landau-Ginzburg-type models, which should be derivable from the underlying
microscopic description of the system in question. We present a study on
classical density functional theory in three stages of approximation leading to
a specific phase field crystal model, and we discuss the limits of
applicability of the models that result from these approximations. As a test
system we have chosen the three--dimensional suspension of monodisperse hard
spheres. The levels of density functional theory that we discuss are
fundamental measure theory, a second-order Taylor expansion thereof, and a
minimal phase-field crystal model. We have computed coexistence densities,
vacancy concentrations in the crystalline phase, interfacial tensions and
interfacial order parameter profiles, and we compare these quantities to
simulation results. We also suggest a procedure to fit the free parameters of
the phase field crystal model.Comment: 21 page
The Early Crystal Nucleation Process in Hard Spheres shows Synchronised Ordering and Densification
We investigate the early part of the crystal nucleation process in the hard
sphere fluid using data produced by computer simulation. We find that hexagonal
order manifests continuously in the overcompressed liquid, beginning
approximately one diffusion time before the appearance of the first
`solid-like' particle of the nucleating cluster, and that a collective influx
of particles towards the nucleation site occurs simultaneously to the ordering
process: the density increases leading to nucleation are generated by the same
individual particle displacements as the increases in order. We rule out the
presence of qualitative differences in the early nucleation process between
medium and low overcompressions, and also provide evidence against any
separation of translational and orientational order on the relevant
lengthscales
Crystallization in suspensions of hard spheres: A Monte Carlo and Molecular Dynamics simulation study
The crystallization of a metastable melt is one of the most important non
equilibrium phenomena in condensed matter physics, and hard sphere colloidal
model systems have been used for several decades to investigate this process by
experimental observation and computer simulation. Nevertheless, there is still
an unexplained discrepancy between simulation data and experimental nucleation
rate densities. In this paper we examine the nucleation process in hard spheres
using molecular dynamics and Monte Carlo simulation. We show that the
crystallization process is mediated by precursors of low orientational
bond-order and that our simulation data fairly match the experimental data
sets
Entropy production in the non-equilibrium steady states of interacting many-body systems
Entropy production is one of the most important characteristics of
non-equilibrium steady states. We study here the steady-state entropy
production, both at short times as well as in the long-time limit, of two
important classes of non-equilibrium systems: transport systems and
reaction-diffusion systems. The usefulness of the mean entropy production rate
and of the large deviation function of the entropy production for
characterizing non-equilibrium steady states of interacting many-body systems
is discussed. We show that the large deviation function displays a kink-like
feature at zero entropy production that is similar to that observed for a
single particle driven along a periodic potential. This kink is a direct
consequence of the detailed fluctuation theorem fulfilled by the probability
distribution of the entropy production and is therefore a generic feature of
the corresponding large deviation function.Comment: 7 figures, to appear in Physical Review
Posterior probability and fluctuation theorem in stochastic processes
A generalization of fluctuation theorems in stochastic processes is proposed.
The new theorem is written in terms of posterior probabilities, which are
introduced via the Bayes theorem. In usual fluctuation theorems, a forward path
and its time reversal play an important role, so that a microscopically
reversible condition is essential. In contrast, the microscopically reversible
condition is not necessary in the new theorem. It is shown that the new theorem
adequately recovers various theorems and relations previously known, such as
the Gallavotti-Cohen-type fluctuation theorem, the Jarzynski equality, and the
Hatano-Sasa relation, when adequate assumptions are employed.Comment: 4 page
Test of the photon detection system for the LHCb RICH Upgrade in a charged particle beam
The LHCb detector will be upgraded to make more efficient use of the
available luminosity at the LHC in Run III and extend its potential for
discovery. The Ring Imaging Cherenkov detectors are key components of the LHCb
detector for particle identification. In this paper we describe the setup and
the results of tests in a charged particle beam, carried out to assess
prototypes of the upgraded opto-electronic chain from the Multi-Anode PMT
photosensor to the readout and data acquisition system.Comment: 25 pages, 22 figure
Current large deviations in a driven dissipative model
We consider lattice gas diffusive dynamics with creation-annihilation in the
bulk and maintained out of equilibrium by two reservoirs at the boundaries.
This stochastic particle system can be viewed as a toy model for granular gases
where the energy is injected at the boundary and dissipated in the bulk. The
large deviation functional for the particle currents flowing through the system
is computed and some physical consequences are discussed: the mechanism for
local current fluctuations, dynamical phase transitions, the
fluctuation-relation
- …