204 research outputs found
Exactly solvable reaction diffusion models on a Cayley tree
The most general reaction-diffusion model on a Cayley tree with
nearest-neighbor interactions is introduced, which can be solved exactly
through the empty-interval method. The stationary solutions of such models, as
well as their dynamics, are discussed. Concerning the dynamics, the spectrum of
the evolution Hamiltonian is found and shown to be discrete, hence there is a
finite relaxation time in the evolution of the system towards its stationary
state.Comment: 9 pages, 2 figure
Exactly solvable models through the generalized empty interval method: multi-species and more-than-two-site interactions
Multi-species reaction-diffusion systems, with more-than-two-site interaction
on a one-dimensional lattice are considered. Necessary and sufficient
constraints on the interaction rates are obtained, that guarantee the
closedness of the time evolution equation for 's, the
expectation value of the product of certain linear combination of the number
operators on consecutive sites at time .Comment: 10 pages, LaTe
Cluster approximation solution of a two species annihilation model
A two species reaction-diffusion model, in which particles diffuse on a
one-dimensional lattice and annihilate when meeting each other, has been
investigated. Mean field equations for general choice of reaction rates have
been solved exactly. Cluster mean field approximation of the model is also
studied. It is shown that, the general form of large time behavior of one- and
two-point functions of the number operators, are determined by the diffusion
rates of the two type of species, and is independent of annihilation rates.Comment: 9 pages, 7 figure
Static- and dynamical-phase transition in multidimensional voting models on continua
A voting model (or a generalization of the Glauber model at zero temperature)
on a multidimensional lattice is defined as a system composed of a lattice each
site of which is either empty or occupied by a single particle. The reactions
of the system are such that two adjacent sites, one empty the other occupied,
may evolve to a state where both of these sites are either empty or occupied.
The continuum version of this model in a Ddimensional region with boundary is
studied, and two general behaviors of such systems are investigated. The
stationary behavior of the system, and the dominant way of the relaxation of
the system toward its stationary state. Based on the first behavior, the static
phase transition (discontinuous changes in the stationary profiles of the
system) is studied. Based on the second behavior, the dynamical phase
transition (discontinuous changes in the relaxation-times of the system) is
studied. It is shown that the static phase transition is induced by the bulk
reactions only, while the dynamical phase transition is a result of both bulk
reactions and boundary conditions.Comment: 10 pages, LaTeX2
Phase transition in an asymmetric generalization of the zero-temperature Glauber model
An asymmetric generalization of the zero-temperature Glauber model on a
lattice is introduced. The dynamics of the particle-density and specially the
large-time behavior of the system is studied. It is shown that the system
exhibits two kinds of phase transition, a static one and a dynamic one.Comment: LaTeX, 9 pages, to appear in Phys. Rev. E (2001
Exactly solvable models through the empty interval method
The most general one dimensional reaction-diffusion model with
nearest-neighbor interactions, which is exactly-solvable through the empty
interval method, has been introduced. Assuming translationally-invariant
initial conditions, the probability that consecutive sites are empty
(), has been exactly obtained. In the thermodynamic limit, the large-time
behavior of the system has also been investigated. Releasing the translational
invariance of the initial conditions, the evolution equation for the
probability that consecutive sites, starting from the site , are empty
() is obtained. In the thermodynamic limit, the large time behavior of
the system is also considered. Finally, the continuum limit of the model is
considered, and the empty-interval probability function is obtained.Comment: 12 pages, LaTeX2
Phase transition in an asymmetric generalization of the zero-temperature q-state Potts model
An asymmetric generalization of the zero-temperature q-state Potts model on a
one dimensional lattice, with and without boundaries, has been studied. The
dynamics of the particle number, and specially the large time behavior of the
system has been analyzed. In the thermodynamic limit, the system exhibits two
kinds of phase transitions, a static and a dynamic phase transition.Comment: 11 pages, LaTeX2
Connection between matrix-product states and superposition of Bernoulli shock measures
We consider a generalized coagulation-decoagulation system on a
one-dimensional discrete lattice with reflecting boundaries. It is known that a
Bernoulli shock measure with two shock fronts might have a simple random-walk
dynamics, provided that some constraints on the microscopic reaction rates of
this system are fulfilled. Under these constraints the steady-state of the
system can be written as a linear superposition of such shock measures. We show
that the coefficients of this expansion can be calculated using the
finite-dimensional representation of the quadratic algebra of the system
obtained from a matrix-product approach.Comment: 5 page
Finite-dimensional representation of the quadratic algebra of a generalized coagulation-decoagulation model
The steady-state of a generalized coagulation-decoagulation model on a
one-dimensional lattice with reflecting boundaries is studied using a
matrix-product approach. It is shown that the quadratic algebra of the model
has a four-dimensional representation provided that some constraints on the
microscopic reaction rates are fulfilled. The dynamics of a product shock
measure with two shock fronts, generated by the Hamiltonian of this model, is
also studied. It turns out that the shock fronts move on the lattice as two
simple random walkers which repel each other provided that the same constraints
on the microscopic reaction rates are satisfied.Comment: Minor revision
Autonomous multispecies reaction-diffusion systems with more-than-two-site interactions
Autonomous multispecies systems with more-than-two-neighbor interactions are
studied. Conditions necessary and sufficient for closedness of the evolution
equations of the -point functions are obtained. The average number of the
particles at each site for one species and three-site interactions, and its
generalization to the more-than-three-site interactions is explicitly obtained.
Generalizations of the Glauber model in different directions, using generalized
rates, generalized number of states at each site, and generalized number of
interacting sites, are also investigated.Comment: 9 pages, LaTeX2
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