Showing papers by "Andreas Schadschneider published in 2005"

Intracellular Transport of Single-Headed Molecular Motors KIF1A

Abstract: Motivated by experiments on single-headed kinesin KIF1A, we develop a model of intracellular transport by interacting molecular motors. It captures explicitly not only the effects of adenosine triphosphate hydrolysis, but also the ratchet mechanism which drives individual motors. Our model accounts for the experimentally observed single-molecule properties in the low-density limit and also predicts a phase diagram that shows the influence of hydrolysis and Langmuir kinetics on the collective spatiotemporal organization of the motors. Finally, we provide experimental evidence for the existence of domain walls in our in vitro experiment with fluorescently labeled KIF1A.

Asymmetric exclusion processes with shuffled dynamics

Abstract: The asymmetric simple exclusion process (ASEP) with periodic boundary conditions is investigated for shuffled dynamics. In this type of update, in each discrete timestep the particles are updated in a random sequence. Such an update is important for several applications, e.g. for certain models of pedestrian flow in two dimensions. For the ASEP with shuffled dynamics and a related truncated process exact results are obtained for deterministic motion (p=1). Since the shuffled dynamics is intrinsically stochastic, also this case is nontrivial. For the case of stochastic motion (0

Optimization of Highway Networks and Traffic Forecasting

Abstract: The understanding of traffic dynamics on highway networks is essential for traffic control. Nowadays realistic microscopic models exist that allow highly efficient (faster-than-real-time) simulations of large networks. These simulations can be used not only to determine the state of the network from incomplete information, but also for traffic forecasting. We also discuss an analysis of the highway network in Germany to identify bottlenecks and possible optimization strategies. Language: en

Simulations of Evacuation by an Extended Floor Field CA Model

Abstract: The floor field CA model for studying evacuation dynamics is extended in this paper. A method for calculating the static floor field, which describes the shortest distance to an exit door, in an arbitrary geometry of rooms is presented. The wall potential and contraction effect at a wide exit are also proposed in order to obtain realistic behavior near corners and bottlenecks.

Adaptive Traffic Light Control in the ChSch Model for City Traffic

Abstract: The impact of adaptive traffic light control is studied in the Chowdhury Schadschneider (ChSch) cellular automaton (CA) model for city traffic. Therefore, three adaptive strategies are presented being able to react flexible to the traffic conditions. It is shown that the adaptive control is capable to direct the system to its system optimum. Furthermore, the impact inhomogeneous densities is investigated with the aim to demonstrate the difference between a global traffic control and an adaptive one if varying traffic conditions are considered.

Exact ground states of quantum spin-2 models on the hexagonal lattice

Abstract: We construct exact non-trivial ground states of spin-2 quantum antiferromagnets on the hexagonal lattice. Using the optimum ground state approach we determine the ground state in different subspaces of a general spin-2 Hamiltonian consistent with some realistic symmetries. These states, which are not of simple product form, depend on two free parameters and can be shown to be only weakly degenerate. We find ground states with different types of magnetic order, i.e. a weak antiferromagnet with finite sublattice magnetization and a weak ferromagnet with ferrimagnetic order. For the latter it is argued that a quantum phase transition occurs within the solvable subspace.

Optimization Potential of a Highway Network: An Empirical Study

Abstract: We present an analysis of traffic data of the highway network of North-Rhine-Westphalia in order to identify and characterize the sections of the network which limit the performance, i.e., the bottlenecks. It is clarified whether the bottlenecks are of topological nature or if they are constituted by on-ramps. This allows to judge possible optimization mechanisms and reveals in which areas of the network they have to be applied. Our results support previous empirical observations and theoretical studies indicating that the overall travel-time of vehicles in a traffic network can be optimized by means of ramp metering control systems.

Anomalous Fundamental Diagrams in Traffic on Ant Trails

Abstract: Many insects like ants communicate chemically via chemotaxis. This allows them to build large trail systems which in many respects are similar to human-build highway networks. Using a stochastic cellular automaton model we discuss the basic properties of the traffic flow on existing trails. Surprisingly it is found that in certain regimes the average speed of the ants can vary non-monotonically with their density. This is in sharp contrast to highway traffic. The observations can be understood by the formation of loose clusters, i.e. space regions of enhanced, but not maximal, density. We also discuss the effect of counterflow on the trails.

Phase Diagrams of an Internet Model with Multi-Allocation of Sites

Abstract: A recently introduced cellular automaton model for Internet traffic is investigated in the context of boundary induced phase transitions and the appropriate phase diagrams. Since the model allows multi allocation of sites there are some deviations in the internal dynamics as well as in global properties compared to known driven lattice gas models. As a consequence the yielding phase diagram derived by numerical simulations reveals some interesting new features like a capacity shift in dependence to the allocation number.