Research Topics


Universal scaling behavior of non-equilibrium phase transitions

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)


Crossover phenomena in continuous phase transitions

Subject of the investigations is the scaling behavior of various
crossover phenomena, including crossovers i) of ordinary
critical behavior to tricritical behavior, ii) crossovers from
short-range to long-range interactions, iii) crossover between
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)


Driven interfaces in disordered magnetic systems

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)


Statistical physics of traffic flow models

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)


Selforganized criticality in driven dissipative systems

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 in dynamical systems


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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