Logarithmic roughening in a growth process with edge evaporation

Roughening transitions are often characterized by unusual scaling properties. As an example we investigate the roughening transition in a solid-on-solid growth process with edge evaporation [Phys. Rev. Lett. 76, 2746 (1996)], where the interface is known to roughen logarithmically with time. Performing high-precision simulations we find appropriate scaling forms for various quantities. Moreover we present a simple approximation explaining why the interface roughens logarithmically.Comment: revtex, 6 pages, 7 eps figure

CAVIAR: Climate variability of the Baltic Sea area and the response of the general circulation of the Baltic Sea to climate variability

The warming trend for the entire globe (1850-2005) is 0.04°C per decade. A specific warming period started around 1980 and continues at least until 2005, with a temperature increase of about 0.17°C per decade. This trend is equally well evident for many areas on the globe, especially on the northern hemisphere in observations and climate simulations. For the Baltic Sea catchment, which lies between maritime temperate and continental sub-Arctic climate zones, an even stronger warming of about 0.4°C per decade appeared since 1980. The annual mean air temperature increased by about 1°C until 2004. A similar warming trend could be observed for the sea surface temperature of the Baltic Sea. Even the annual mean water temperatures averaged spatially and vertically for the deep basins of the Baltic Sea show similar trends. We provide a detailed analysis of the climate variability and associated changes in the Baltic Sea catchment area as well as in the Baltic Sea itself for the period 1958-2009, in which the recent acceleration of the climate warming happened. Changes in the atmospheric conditions causes corresponding changes in the Baltic Sea, not only for temperature and salinity but also for currents and circulation. These changes in the physical conditions have strong impact on the marine ecosystem structure and processes

On the predictive power of Local Scale Invariance

Local Scale Invariance (LSI) is a theory for anisotropic critical phenomena designed in the spirit of conformal invariance. For a given representation of its generators it makes non-trivial predictions about the form of universal scaling functions. In the past decade several representations have been identified and the corresponding predictions were confirmed for various anisotropic critical systems. Such tests are usually based on a comparison of two-point quantities such as autocorrelation and response functions. The present work highlights a potential problem of the theory in the sense that it may predict any type of two-point function. More specifically, it is argued that for a given two-point correlator it is possible to construct a representation of the generators which exactly reproduces this particular correlator. This observation calls for a critical examination of the predictive content of the theory.Comment: 17 pages, 2 eps figure

A Generalized Duality Transformation of the Anisotropic Xy Chain in a Magnetic Field

We consider the anisotropic $XY$ chain in a magnetic field with special boundary conditions described by a two-parameter Hamiltonian. It is shown that the exchange of the parameters corresponds to a similarity transformation, which reduces in a special limit to the Ising duality transformation.Comment: 6 pages, LaTeX, BONN-HE-93-4

Nonequilibrium critical behavior of a species coexistence model

A biologically motivated model for spatio-temporal coexistence of two competing species is studied by mean-field theory and numerical simulations. In d>1 dimensions the phase diagram displays an extended region where both species coexist, bounded by two second-order phase transition lines belonging to the directed percolation universality class. The two transition lines meet in a multicritical point, where a non-trivial critical behavior is observed.Comment: 11 page

Universality class of the pair contact process with diffusion

The pair contact process with diffusion (PCPD) is studied with a standard Monte Carlo approach and with simulations at fixed densities. A standard analysis of the simulation results, based on the particle densities or on the pair densities, yields inconsistent estimates for the critical exponents. However, if a well-chosen linear combination of the particle and pair densities is used, leading corrections can be suppressed, and consistent estimates for the independent critical exponents delta=0.16(2), beta=0.28(2) and z=1.58 are obtained. Since these estimates are also consistent with their values in directed percolation (DP), we conclude that PCPD falls in the same universality class as DP.Comment: 8 pages, 8 figures, accepted by Phys. Rev. E (not yet published

Matrix Product Eigenstates for One-Dimensional Stochastic Models and Quantum Spin Chains

We show that all zero energy eigenstates of an arbitrary $m$--state quantum spin chain Hamiltonian with nearest neighbor interaction in the bulk and single site boundary terms, which can also describe the dynamics of stochastic models, can be written as matrix product states. This means that the weights in these states can be expressed as expectation values in a Fock representation of an algebra generated by $2m$ operators fulfilling $m^2$ quadratic relations which are defined by the Hamiltonian.Comment: 11 pages, Late

Pair contact process with diffusion - A new type of nonequilibrium critical behavior?

Recently Carlon et. al. investigated the critical behavior of the pair contact process with diffusion [cond-mat/9912347]. Using density matrix renormalization group methods, they estimate the critical exponents, raising the possibility that the transition might belong to the same universality class as branching annihilating random walks with even numbers of offspring. This is surprising since the model does not have an explicit parity-conserving symmetry. In order to understand this contradiction, we estimate the critical exponents by Monte Carlo simulations. The results suggest that the transition might belong to a different universality class that has not been investigated before.Comment: RevTeX, 3 pages, 2 eps figures, adapted to final version of cond-mat/991234

Differences between regular and random order of updates in damage spreading simulations

We investigate the spreading of damage in the three-dimensional Ising model by means of large-scale Monte-Carlo simulations. Within the Glauber dynamics we use different rules for the order in which the sites are updated. We find that the stationary damage values and the spreading temperature are different for different update order. In particular, random update order leads to larger damage and a lower spreading temperature than regular order. Consequently, damage spreading in the Ising model is non-universal not only with respect to different update algorithms (e.g. Glauber vs. heat-bath dynamics) as already known, but even with respect to the order of sites.Comment: final version as published, 4 pages REVTeX, 2 eps figures include

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.Comment: 4 pages, 3 figure