219 research outputs found
Scaling behavior of the conserved transfer threshold process
We analyze numerically the critical behavior of an absorbing phase transition
in the conserved transfer threshold process. We determined the steady state
scaling behavior of the order parameter as a function of both, the control
parameter and an external field, conjugated to the order parameter. The
external field is realized as a spontaneous creation of active particles which
drives the system away from criticality. The obtained results yields that the
conserved transfers threshold process belongs to the universality class of
absorbing phase transitions in a conserved field.Comment: 6 pages, 8 figures, accepted for publication in Phys. Rev.
Cloning and characterization of the Yersinia enterocolitica serotype O:9 lipopolysaccharide O-antigen gene cluster
Mean-field scaling function of the universality class of absorbing phase transitions with a conserved field
We consider two mean-field like models which belong to the universality class
of absorbing phase transitions with a conserved field. In both cases we derive
analytically the order parameter as function of the control parameter and of an
external field conjugated to the order parameter. This allows us to calculate
the universal scaling function of the mean-field behavior. The obtained
universal function is in perfect agreement with recently obtained numerical
data of the corresponding five and six dimensional models, showing that four is
the upper critical dimension of this particular universality class.Comment: 8 pages, 2 figures, accepted for publication in J. Phys.
Moment analysis of the probability distributions of different sandpile models
We reconsider the moment analysis of the Bak-Tang-Wiesenfeld and the Manna
sandpile model in two and three dimensions. In contrast to recently performed
investigations our analysis turns out that the models are characterized by
different scaling behavior, i.e., they belong to different universality
classes.Comment: 6 pages, 6 figures, accepted for publication in Physical Review
Absorbing phase transition in a conserved lattice gas with random neighbor particle hopping
A conserved lattice gas with random neighbor hopping of active particles is
introduced which exhibits a continuous phase transition from an active state to
an absorbing non-active state. Since the randomness of the particle hopping
breaks long range spatial correlations our model mimics the mean-field scaling
behavior of the recently introduced new universality class of absorbing phase
transitions with a conserved field. The critical exponent of the order
parameter is derived within a simple approximation. The results are compared
with those of simulations and field theoretical approaches.Comment: 5 pages, 3 figures, accepted for publication in J. Phys.
Crossover phenomenon in self-organized critical sandpile models
We consider a stochastic sandpile where the sand-grains of unstable sites are
randomly distributed to the nearest neighbors. Increasing the value of the
threshold condition the stochastic character of the distribution is lost and a
crossover to the scaling behavior of a different sandpile model takes place
where the sand-grains are equally transferred to the nearest neighbors. The
crossover behavior is numerically analyzed in detail, especially we consider
the exponents which determine the scaling behavior.Comment: 6 pages, 9 figures, accepted for publication in Physical Review
Tricritical directed percolation
We consider a modification of the contact process incorporating higher-order
reaction terms. The original contact process exhibits a non-equilibrium phase
transition belonging to the universality class of directed percolation. The
incorporated higher-order reaction terms lead to a non-trivial phase diagram.
In particular, a line of continuous phase transitions is separated by a
tricritical point from a line of discontinuous phase transitions. The
corresponding tricritical scaling behavior is analyzed in detail, i.e., we
determine the critical exponents, various universal scaling functions as well
as universal amplitude combinations
Logarithmic corrections of the avalanche distributions of sandpile models at the upper critical dimension
We study numerically the dynamical properties of the BTW model on a square
lattice for various dimensions. The aim of this investigation is to determine
the value of the upper critical dimension where the avalanche distributions are
characterized by the mean-field exponents. Our results are consistent with the
assumption that the scaling behavior of the four-dimensional BTW model is
characterized by the mean-field exponents with additional logarithmic
corrections. We benefit in our analysis from the exact solution of the directed
BTW model at the upper critical dimension which allows to derive how
logarithmic corrections affect the scaling behavior at the upper critical
dimension. Similar logarithmic corrections forms fit the numerical data for the
four-dimensional BTW model, strongly suggesting that the value of the upper
critical dimension is four.Comment: 8 pages, including 9 figures, accepted for publication in Phys. Rev.
The Bak-Tang-Wiesenfeld sandpile model around the upper critical dimension
We consider the Bak-Tang-Wiesenfeld sandpile model on square lattices in
different dimensions (D>=6). A finite size scaling analysis of the avalanche
probability distributions yields the values of the distribution exponents, the
dynamical exponent, and the dimension of the avalanches. Above the upper
critical dimension D_u=4 the exponents equal the known mean field values. An
analysis of the area probability distributions indicates that the avalanches
are fractal above the critical dimension.Comment: 7 pages, including 9 figures, accepted for publication in Physical
Review
Mean-field behavior of the sandpile model below the upper critical dimension
We present results of large scale numerical simulations of the Bak, Tang and
Wiesenfeld sandpile model. We analyze the critical behavior of the model in
Euclidean dimensions . We consider a dissipative generalization
of the model and study the avalanche size and duration distributions for
different values of the lattice size and dissipation. We find that the scaling
exponents in significantly differ from mean-field predictions, thus
suggesting an upper critical dimension . Using the relations among
the dissipation rate and the finite lattice size , we find that a
subset of the exponents displays mean-field values below the upper critical
dimensions. This behavior is explained in terms of conservation laws.Comment: 4 RevTex pages, 2 eps figures embedde
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