Research Topics

Similar to equilibrium critical phenomena, the concept of

universality remains the major tool to order the great variety of

non-equilibrium phase transitions systematically. All systems

belonging to a given universality class share the same set of

critical exponents, and certain scaling functions become identical

near the critical point. It is known that scaling functions vary more

widely between different universality classes than the usually

determined exponents do. The aim of the investigations is to obtain a

picture gallery of scaling functions of various non-equilibrium

universality classes. This is of fundamental interest since a general

classification scheme of non-equilibrium phase transitions is still

unknown.

(16 publications)

Subject of the investigations is the scaling behavior of various

crossover phenomena, including crossovers

critical behavior to tricritical behavior,

short-range to long-range interactions,

different universality classes. Using computer simulations, we

show that crossover scaling functions are universal and that

the effective exponents violate the so-called scaling laws. Recently

performed analyz es focus on the determination of the size of the

crossover regime and address the question how corrections to

the leading order affects the crossover scaling behavior. All

results are of experimental relevance and are valid in equilibrium

as well as in non-equilibrium systems.

(5 publications)

Interfaces in quenched disordered systems display with increasing

driving force a transition from a pinned interphase to a moving

interface. Besides the analysis of the order parameter behavior we

investigate how thermal fluctuations affect this depinning transition

These thermal fluctuations are usually neglected although they are of

great importance for the interpretation of experimental data, in

particular within the so-called creep regime.

(5 publications)

Real traffic displays with increasing car density a transition from

free flow to congested traffic. This break down of free flow traffic

is accompanied by the occurrence of traffic jams, i.e., backward

moving density fluctuations. We developed a method which allows to

characterize the jammed traffic phase via collective coordinates. In

that way, we determined how various fundamental system parameters

affected the transition from the free traffic flow to the congested

traffic.

(4 publications)

Self-organized criticality (SOC) refers to driven-dissipative systems

that naturally evolve to a critical state, characterized by scale

invariant distributions of relaxation events. The self-organization

to the critical point distinguishes SOC from ordinary critical

phenomena where a temperature-like variable has to be fine-tuned to

the critical point. Besides of analysis of the scaling behavior of

avalanche-like relaxation processes, we examine the still incompletely

understood selforganization to the critical point.

(10 publications)

Synchronization phenomena attract a lot of attention in the last

years due to its ubiquity (including phenomena in physics, biology,

as well as in socio-economic systems. A mechanical exemplification

are synchronized metronomes coupled by a moving base. Thus the

synchronization can be investigated analytically, experimentally,

as well as numerically.

(Movies of synchronized metronomes)

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