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D. Mukamel

Publications and source records attributed to D. Mukamel.

At least 37 records · Page 2Linked to original sources
arXiv2004

Zero-range process with open boundaries

We calculate the exact stationary distribution of the one-dimensional zero-range process with open boundaries for arbitrary bulk and boundary hopping rates. When such a distribution exists, the steady state has no correlations between sites and is uniquely characterized by a space-dependent fugacity which is a function of the boundary rates and the hopping asymmetry. For strong boundary drive the system has no stationary distribution. In systems which on a ring geometry allow for a condensation transition, a condensate develops at one or both boundary sites. On all other sites the particle distribution approaches a product measure with the finite critical density ρ_c. In systems which do not support condensation on a ring, strong boundary drive leads to a condensate at the boundary. However, in this case the local particle density in the interior exhibits a complex algebraic growth in time. We calculate the bulk and boundary growth exponents as a function of the system parameters.

cond-mat.stat-mech↗
arXiv2004

Long-range attraction between probe particles mediated by a driven fluid

The effective interaction between two probe particles in a one-dimensional driven system is studied. The analysis is carried out using an asymmetric simple exclusion process with nearest-neighbor interactions. It is found that the driven fluid mediates an effective long-range attraction between the two probes, with a force that decays at large distances x as -b/x, where b is a function of the interaction parameters. Depending on the amplitude b the two probes may form one of three states: (a) an unbound state, where the distance grows diffusively with time; (b) a weakly bound state, in which the distance grows sub-diffusively; and (c) a strongly bound state, where the average distance stays finite in the long time limit. Similar results are found for the behavior of any finite number of probes.

cond-mat.stat-mech↗
arXiv2004

Modelling one-dimensional driven diffusive systems by the Zero-Range Process

The recently introduced correspondence between one-dimensional two-species driven models and the Zero-Range Process is extended to study the case where the densities of the two species need not be equal. The correspondence is formulated through the length dependence of the current emitted from a particle domain. A direct numerical method for evaluating this current is introduced, and used to test the assumptions underlying this approach. In addition, a model for isolated domain dynamics is introduced, which provides a simple way to calculate the current also for the non-equal density case. This approach is demonstrated and applied to a particular two-species model, where a phase separation transition line is calculated.

cond-mat.stat-mech↗
arXiv2004

Condensation transition in zero-range processes with diffusion

Recent studies have indicated that the coarse grained dynamics of a large class of traffic models and driven-diffusive systems may be described by urn models. We consider a class of one-dimensional urn models whereby particles hop from an urn to its nearest neighbor by a rate which decays with the occupation number k of the departure site as (1+b/k). In addition a diffusion process takes place, whereby all particles in an urn may hop to an adjacent one with some rate alpha$. Condensation transition which may take place in this model is studied and the (b,alpha) phase diagram is calculated within the mean field approximation and by numerical simulations. A driven-diffusive model whose coarse grained dynamics corresponds to this urn model is considered.

cond-mat.stat-mech↗
arXiv2004

Traffic jams and ordering far from thermal equilibrium

The recently suggested correspondence between domain dynamics of traffic models and the asymmetric chipping model is reviewed. It is observed that in many cases traffic domains perform the two characteristic dynamical processes of the chipping model, namely chipping and diffusion. This correspondence indicates that jamming in traffic models in which all dynamical rates are non-deterministic takes place as a broad crossover phenomenon, rather than a sharp transition. Two traffic models are studied in detail and analyzed within this picture.

cond-mat.stat-mech↗
arXiv2004

Hard Disks in Narrow Channels

The thermodynamic and dynamical behavior of a gas of hard disks in a narrow channel is studied theoretically and numerically. Using a virial expansion we find that the pressure and collision frequency curves exhibit a singularity at a channel width corresponding to twice the disk diameter. As expected, the maximum Lyapunov exponent is also found to display a similar behavior. At high density these curves are dominated by solid-like configurations which are different from the bulk ones, due to the channel boundary conditions.

cond-mat.stat-mech↗
arXiv2004

Condensation Transitions in a One-Dimensional Zero-Range Process with a Single Defect Site

Condensation occurs in nonequilibrium steady states when a finite fraction of particles in the system occupies a single lattice site. We study condensation transitions in a one-dimensional zero-range process with a single defect site. The system is analysed in the grand canonical and canonical ensembles and the two are contrasted. Two distinct condensation mechanisms are found in the grand canonical ensemble. Discrepancies between the infinite and large but finite systems' particle current versus particle density diagrams are investigated and an explanation for how the finite current goes above a maximum value predicted for infinite systems is found in the canonical ensemble.

cond-mat.stat-mech↗
arXiv2003

Phase Transitions in Traffic Models

It is suggested that the question of existence of a jamming phase transition in a broad class of single-lane cellular-automaton traffic models may be studied using a correspondence to the asymmetric chipping model. In models where such correspondence is applicable, jamming phase transition does not take place. Rather, the system exhibits a smooth crossover between free-flow and jammed states, as the car density is increased.

cond-mat.stat-mech↗
arXiv2003

From multiplicative noise to directed percolation in wetting transitions

A simple one-dimensional microscopic model of the depinning transition of an interface from an attractive hard wall is introduced and investigated. Upon varying a control parameter, the critical behaviour observed along the transition line changes from a directed-percolation to a multiplicative-noise type. Numerical simulations allow for a quantitative study of the multicritical point separating the two regions, Mean-field arguments and the mapping on a yet simpler model provide some further insight on the overall scenario.

cond-mat.stat-mech↗
arXiv2003

Wetting under non-equilibrium conditions

We report a detailed account of the phase diagram of a recently introduced model for non-equilibrium wetting in 1+1 dimensions [Phys. Rev. Lett. 79, 2710 (1997)]. A mean field approximation is shown to reproduce the main features of the phase diagram, while providing indications for the behaviour of the wetting transition in higher dimensions. The mean field phase diagram is found to exhibit an extra transition line which does not exist in 1+1 dimensions. The line separates a phase in which the interface height distribution decays exponentially at large heights, from a superexponentially decaying phase. Implications to wetting in dimensions higher than 1+1 are discussed.

cond-mat.stat-mech↗
arXiv2002

Griffiths singularities in unbinding of strongly disordered polymers

Griffiths singularities occurring in the unbinding of strongly disordered heteropolymers are studied. A model with two randomly distributed binding energies -1 and -v, is introduced and studied analytically by analyzing the Lee-Yang zeros of the partition sum. It is demonstrated that in the limit v -> infinity the model exhibits a Griffiths type singularity at a temperature T_G =O(1) corresponding to melting of long homogeneous domains of the low binding energy. For finite v >> 1 the model is expected to exhibit an additional, unbinding, transition at a high temperature T_M=O(v).

cond-mat.stat-mech↗
arXiv2002

Novel phase-separation transition in one-dimensional driven models

A class of models of driven diffusive systems which is shown to exhibit phase separation in $d=1$ dimensions is introduced. Unlike all previously studied models exhibiting similar phenomena, here the phase separated state is fluctuating in the bulk of the macroscopic domains. The nature of the phase transition from the homogeneous to the phase separated state is discussed in view of a recently introduced criterion for phase separation in one-dimensional driven systems.

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arXiv2002

Inter-strand distance distribution of DNA near melting

The distance distribution between complementary base pairs of the two strands of a DNA molecule is studied near the melting transition. Scaling arguments are presented for a generalized Poland-Scheraga type model which includes self-avoiding interactions. At the transition temperature and for a large distance r the distribution decays as 1/r^κwith κ=1+(c-2)/ ν. Here νis the self-avoiding walk correlation length exponent and c is the exponent associated with the entropy of an open loop in the chain. Results for the distribution function just below the melting point are also presented. Numerical simulations which fully take into account the self-avoiding interactions are in good agreement with the scaling approach.

cond-mat.stat-mech↗
arXiv2002

Criterion for phase separation in one-dimensional driven systems

A general criterion for the existence of phase separation in driven one-dimensional systems is proposed. It is suggested that phase separation is related to the size dependence of the steady-state currents of domains in the system. A quantitative criterion for the existence of phase separation is conjectured using a correspondence made between driven diffusive models and zero-range processes. Several driven diffusive models are discussed in light of the conjecture.

cond-mat.stat-mech↗
arXiv2002

Sharp crossover and anomalously large correlation length in driven systems

Models of one-dimensional driven diffusive systems sometimes exhibit an abrupt increase of the correlation length to an anomalously large but finite value as the parameters of the model are varied. This behavior may be misinterpreted as a genuine phase transition. A simple mechanism for this sharp increase is presented. The mechanism is introduced within the framework of a recently suggested correspondence between driven diffusive systems and zero-range processes. It is shown that when the dynamics of the model is such that small domains are suppressed in the steady-state distribution, anomalously large correlation length may build up. The mechanism is examined in detail in two models.

cond-mat.stat-mech↗
arXiv2002

Phase transition in a non-conserving driven diffusive system

An asymmetric exclusion process comprising positive particles, negative particles and vacancies is introduced. The model is defined on a ring and the dynamics does not conserve the number of particles. We solve the steady state exactly and show that it can exhibit a continuous phase transition in which the density of vacancies decreases to zero. The model has no absorbing state and furnishes an example of a one-dimensional phase transition in a homogeneous non-conserving system which does not belong to the absorbing state universality classes.

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