319 research outputs found
Discontinuous Phase Transition in an Exactly Solvable One-Dimensional Creation-Annihilation System
An exactly solvable reaction-diffusion model consisting of first-class
particles in the presence of a single second-class particle is introduced on a
one-dimensional lattice with periodic boundary condition. The number of
first-class particles can be changed due to creation and annihilation
reactions. It is shown that the system undergoes a discontinuous phase
transition in contrast to the case where the density of the second-class
particles is finite and the phase transition is continuous.Comment: Revised, 8 pages, 1 EPS figure. Accepted for publication in Journal
of Statistical Mechanics: theory and experimen
Phase Transition in a Three-States Reaction-Diffusion System
A one-dimensional reaction-diffusion model consisting of two species of
particles and vacancies on a ring is introduced. The number of particles in one
species is conserved while in the other species it can fluctuate because of
creation and annihilation of particles. It has been shown that the model
undergoes a continuous phase transition from a phase where the currents of
different species of particles are equal to another phase in which they are
different. The total density of particles and also their currents in each phase
are calculated exactly.Comment: 6 page
Exact Solution of an Exclusion Model in the Presence of a moving Impurity
We study a recently introduced model which consists of positive and negative
particles on a ring. The positive (negative) particles hop clockwise
(counter-clockwise) with rate 1 and oppositely charged particles may swap their
positions with asymmetric rates q and 1. In this paper we assume that a finite
density of positively charged particles and only one negative particle
(which plays the role of an impurity) exist on the ring. It turns out that the
canonical partition function of this model can be calculated exactly using
Matrix Product Ansatz (MPA) formalism. In the limit of infinite system size and
infinite number of positive particles, we can also derive exact expressions for
the speed of the positive and negative particles which show a second order
phase transition at . The density profile of the positive particles
on the ring has a shock structure for and an exponential behaviour
with correlation length for . It will be shown that the
mean-field results become exact at q=3 and no phase transition occurs for q>2.Comment: 9 pages,4 EPS figures. To be appear in JP
First Order Phase Transition in a Reaction-Diffusion Model With Open Boundary: The Yang-Lee Theory Approach
A coagulation-decoagulation model is introduced on a chain of length L with
open boundary. The model consists of one species of particles which diffuse,
coagulate and decoagulate preferentially in the leftward direction. They are
also injected and extracted from the left boundary with different rates. We
will show that on a specific plane in the space of parameters, the steady state
weights can be calculated exactly using a matrix product method. The model
exhibits a first-order phase transition between a low-density and a
high-density phase. The density profile of the particles in each phase is
obtained both analytically and using the Monte Carlo Simulation. The two-point
density-density correlation function in each phase has also been calculated. By
applying the Yang-Lee theory we can predict the same phase diagram for the
model. This model is further evidence for the applicability of the Yang-Lee
theory in the non-equilibrium statistical mechanics context.Comment: 10 Pages, 3 Figures, To appear in Journal of Physics A: Mathematical
and Genera
The Study of Shocks in Three-States Driven-Diffusive Systems: A Matrix Product Approach
We study the shock structures in three-states one-dimensional
driven-diffusive systems with nearest neighbors interactions using a matrix
product formalism. We consider the cases in which the stationary probability
distribution function of the system can be written in terms of superposition of
product shock measures. We show that only three families of three-states
systems have this property. In each case the shock performs a random walk
provided that some constraints are fulfilled. We calculate the diffusion
coefficient and drift velocity of shock for each family.Comment: 15 pages, Accepted for publication in Journal of Statistical
Mechanics: Theory and Experiment (JSTAT
Equivalence of a one-dimensional driven-diffusive system and an equilibrium two-dimensional walk model
It is known that a single product shock measure in some of one-dimensional
driven-diffusive systems with nearest-neighbor interactions might evolve in
time quite similar to a random walker moving on a one-dimensional lattice with
reflecting boundaries. The non-equilibrium steady-state of the system in this
case can be written in terms of a linear superposition of such uncorrelated
shocks. Equivalently, one can write the steady-state of this system using a
matrix-product approach with two-dimensional matrices. In this paper we
introduce an equilibrium two-dimensional one-transit walk model and find its
partition function using a transfer matrix method. We will show that there is a
direct connection between the partition functions of these two systems. We will
explicitly show that in the steady-state the transfer matrix of the one-transit
walk model is related to the matrix representation of the algebra of the
driven-diffusive model through a similarity transformation. The physical
quantities are also related through the same transformation.Comment: 5 pages, 2 figures, Revte
Identification of Turnip mosaic virus isolated from canola in northeast area of Iran
During March and April of 2011, 436 samples showing viral disease symptoms were collected from canola fields in the Khorasan Razavi province. The samples were tested by double-antibody sandwich (DAS)-enzyme linked immunosorbent assay (ELISA) for the presence of Turnip mosaic virus (TuMV). Among the 436 samples, 117 samples were found to be infected with TuMV. One of the infected samples from Govareshk region (TuMV-IRN GSK) was selected for biological purification. Total RNA of this isolate were extracted and reverse transcriptase (RT)-PCR was performed with specific primers according to the coat protein gene. PCR products (986 bp) was first purified and then directly sequenced. Phylogenetic analyses based on ClustalW multiple alignments with previously reported 33 isolates indicated 88 to 98% similarity in nucleotide and 94 to 99% in amino acid levels among isolates. TuMV-IRN GSK represented the highest identity to another Iranian isolate (IRN TRa6). Phylogenetic tree clustered all sequences into four groups and IRN GSK fell into the basal-B group. Nucleotide and amino acid distances between IRN GSK and other isolates in the basal-B group showed that this isolate was closely related to another Iranian isolate IRN TRa6, and distinct from other isolates in the basal-B group. These results indicate that TuMV is a common pathogen of canola crops in the Khorasan Razavi province.Key words: Turnip mosaic virus (TuMV), canola, reverse-transcription polymerase chain reaction (RT-PCR), coat protein gene, sequence analysis
One-transit paths and steady-state of a non-equilibrium process in a discrete-time update
We have shown that the partition function of the Asymmetric Simple Exclusion
Process with open boundaries in a sublattice-parallel updating scheme is equal
to that of a two-dimensional one-transit walk model defined on a diagonally
rotated square lattice. It has been also shown that the physical quantities
defined in these systems are related through a similarity transformation.Comment: 8 pages, 2 figure
Exact Shock Profile for the ASEP with Sublattice-Parallel Update
We analytically study the one-dimensional Asymmetric Simple Exclusion Process
(ASEP) with open boundaries under sublattice-parallel updating scheme. We
investigate the stationary state properties of this model conditioned on
finding a given particle number in the system. Recent numerical investigations
have shown that the model possesses three different phases in this case. Using
a matrix product method we calculate both exact canonical partition function
and also density profiles of the particles in each phase. Application of the
Yang-Lee theory reveals that the model undergoes two second-order phase
transitions at critical points. These results confirm the correctness of our
previous numerical studies.Comment: 12 pages, 3 figures, accepted for publication in Journal of Physics
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