298 research outputs found
Localized defects in a cellular automaton model for traffic flow with phase separation
We study the impact of a localized defect in a cellular automaton model for
traffic flow which exhibits metastable states and phase separation. The defect
is implemented by locally limiting the maximal possible flow through an
increase of the deceleration probability. Depending on the magnitude of the
defect three phases can be identified in the system. One of these phases shows
the characteristics of stop-and-go traffic which can not be found in the model
without lattice defect. Thus our results provide evidence that even in a model
with strong phase separation stop-and-go traffic can occur if local defects
exist. From a physical point of view the model describes the competition
between two mechanisms of phase separation.Comment: 14 pages, 7 figure
A multi-species asymmetric simple exclusion process and its relation to traffic flow
Using the matrix product formalism we formulate a natural p-species
generalization of the asymmetric simple exclusion process. In this model
particles hop with their own specific rate and fast particles can overtake slow
ones with a rate equal to their relative speed. We obtain the algebraic
structure and study the properties of the representations in detail. The
uncorrelated steady state for the open system is obtained and in the ( limit, the dependence of its characteristics on the distribution of
velocities is determined. It is shown that when the total arrival rate of
particles exceeds a certain value, the density of the slowest particles rises
abroptly.Comment: some typos corrected, references adde
An Exactly Solvable Two-Way Traffic Model With Ordered Sequential Update
Within the formalism of matrix product ansatz, we study a two-species
asymmetric exclusion process with backward and forward site-ordered sequential
update. This model, which was originally introduced with the random sequential
update, describes a two-way traffic flow with a dynamic impurity and shows a
phase transition between the free flow and traffic jam. We investigate the
characteristics of this jamming and examine similarities and differences
between our results and those with random sequential update.Comment: 25 pages, Revtex, 7 ps file
Two-way traffic flow: exactly solvable model of traffic jam
We study completely asymmetric 2-channel exclusion processes in 1 dimension.
It describes a two-way traffic flow with cars moving in opposite directions.
The interchannel interaction makes cars slow down in the vicinity of
approaching cars in other lane. Particularly, we consider in detail the system
with a finite density of cars on one lane and a single car on the other one.
When the interchannel interaction reaches a critical value, traffic jam
occurs, which turns out to be of first order phase transition. We derive exact
expressions for the average velocities, the current, the density profile and
the - point density correlation functions. We also obtain the exact
probability of two cars in one lane being distance apart, provided there is
a finite density of cars on the other lane, and show the two cars form a weakly
bound state in the jammed phase.Comment: 17 pages, Latex, ioplppt.sty, 11 ps figure
Self Organization and a Dynamical Transition in Traffic Flow Models
A simple model that describes traffic flow in two dimensions is studied. A
sharp {\it jamming transition } is found that separates between the low density
dynamical phase in which all cars move at maximal speed and the high density
jammed phase in which they are all stuck. Self organization effects in both
phases are studied and discussed.Comment: 6 pages, 4 figure
Two-Species Annihilation with Drift: A Model with Continuous Concentration-Decay Exponents
We propose a model for diffusion-limited annihilation of two species, or , where the motion of the particles is subject to a drift. For equal
initial concentrations of the two species, the density follows a power-law
decay for large times. However, the decay exponent varies continuously as a
function of the probability of which particle, the hopping one or the target,
survives in the reaction. These results suggest that diffusion-limited
reactions subject to drift do not fall into a limited number of universality
classes.Comment: 10 pages, tex, 3 figures, also available upon reques
Dynamical Phase Transition in One Dimensional Traffic Flow Model with Blockage
Effects of a bottleneck in a linear trafficway is investigated using a simple
cellular automaton model. Introducing a blockage site which transmit cars at
some transmission probability into the rule-184 cellular automaton, we observe
three different phases with increasing car concentration: Besides the free
phase and the jam phase, which exist already in the pure rule-184 model, the
mixed phase of these two appears at intermediate concentration with
well-defined phase boundaries. This mixed phase, where cars pile up behind the
blockage to form a jam region, is characterized by a constant flow. In the
thermodynamic limit, we obtain the exact expressions for several characteristic
quantities in terms of the car density and the transmission rate. These
quantities depend strongly on the system size at the phase boundaries; We
analyse these finite size effects based on the finite-size scaling.Comment: 14 pages, LaTeX 13 postscript figures available upon
request,OUCMT-94-
Exactly solvable statistical model for two-way traffic
We generalize a recently introduced traffic model, where the statistical
weights are associated with whole trajectories, to the case of two-way flow. An
interaction between the two lanes is included which describes a slowing down
when two cars meet. This leads to two coupled five-vertex models. It is shown
that this problem can be solved by reducing it to two one-lane problems with
modified parameters. In contrast to stochastic models, jamming appears only for
very strong interaction between the lanes.Comment: 6 pages Latex, submitted to J Phys.
Driven Lattice Gases with Quenched Disorder: Exact Results and Different Macroscopic Regimes
We study the effect of quenched spatial disorder on the steady states of
driven systems of interacting particles. Two sorts of models are studied:
disordered drop-push processes and their generalizations, and the disordered
asymmetric simple exclusion process. We write down the exact steady-state
measure, and consequently a number of physical quantities explicitly, for the
drop-push dynamics in any dimensions for arbitrary disorder. We find that three
qualitatively different regimes of behaviour are possible in 1- disordered
driven systems. In the Vanishing-Current regime, the steady-state current
approaches zero in the thermodynamic limit. A system with a non-zero current
can either be in the Homogeneous regime, chracterized by a single macroscopic
density, or the Segregated-Density regime, with macroscopic regions of
different densities. We comment on certain important constraints to be taken
care of in any field theory of disordered systems.Comment: RevTex, 17pages, 18 figures included using psfig.st
Hopping motion of lattice gases through nonsymmetric potentials under strong bias conditions
The hopping motion of lattice gases through potentials without
mirror-reflection symmetry is investigated under various bias conditions. The
model of 2 particles on a ring with 4 sites is solved explicitly; the resulting
current in a sawtooth potential is discussed. The current of lattice gases in
extended systems consisting of periodic repetitions of segments with sawtooth
potentials is studied for different concentrations and values of the bias.
Rectification effects are observed, similar to the single-particle case. A
mean-field approximation for the current in the case of strong bias acting
against the highest barriers in the system is made and compared with numerical
simulations. The particle-vacancy symmetry of the model is discussed.Comment: 8 pages (incl. 6 eps figures); RevTeX 3.
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