The European Physical Journal Special Topics

We study the multi-longitudinal mode instability in purely absorptive optical bistability in the limit of nonlinear absorber much thinner than one wavelength. Under that assumption the dynamical equations are space-independent difference-differential equations which allow for an analysis as simple as for the ring cavity, with two additional parameters related to the position of the absorber in the cavity. Different instability scenarios are found as the relative position varies.

This is a tutorial presentation of special features of galactic disc dynamics, which completes our introduction to galactic dynamics initially presented in [30]. The emphasis is on topics where galactic dynamics and celestial mechanics share common starting points and/or methods of approach. We start by giving some definitions and general notions on the link between observations and dynamical modeling of discs. Then we focus on the application of resonant Hamiltonian perturbation theory in disc resonances. By examining in detail the case of the Inner Lindblad resonance, we demonstrate how resonant perturbation theory leads to an orbital theory of spiral structure in normal galaxies. Passing to barred galaxies, the phase space structure and the role of chaos in the corotation region are analyzed. This is accomplished by a summary of the modern theory of invariant manifolds of unstable periodic orbits in the vicinity of L1 or L2, which can interpret the generation of spiral patterns by chaotic orbits beyond corotation. Some additional topics, potentially important for disc dynamics, are briefly commented.

We are concerned with the dynamical description of the motion of a stochastic micro-swimmer with constant speed and fluctuating orientation in the long time limit by adiabatic elimination of the orientational variable. Starting with the corresponding full set of Langevin equations, we eliminate the memory in the stochastic orientation and obtain a stochastic equation for the position alone in the overdamped limit. An equivalent procedure based on the Fokker-Planck equation is presented as well.

We observed sustained axial flow through tubes immersed in water. The flow was spontaneous; i.e., no pressure gradient was applied. The tubes were made of hydrophilic materials: either the polymer Nafion, or a polyacrylic-acid gel in which a tunnel had been bored. Flow was monitored microscopically, with the aid of particles suspended in the water. The flow appears to be associated with recently discovered interfacial phase of water, which lines the insides of the tubes. This phase of water builds from electromagnetic energy absorbed by water from the surrounding environment [6]. That absorbed energy may power the observed flow.

In this paper, we discuss the existence and uniqueness of solutions for a new class of multi-point boundary value problems of multi-term fractional differential equations by using standard fixed point theorems. We also demonstrate the application of the obtained results with the aid of examples. The paper concludes with the study of multi-term fractional integro-differential equations supplemented with multi-point boundary conditions. Our results are new and contribute significantly to the existing literature on the topic.

With the emergence of the CAN (Coherent Amplification Network) laser technology, a new scheme for direct particle acceleration in periodic plasma structures has been proposed. By using our full electromagnetic relativistic particle-in-cell (PIC) simulation code equipped with ionisation module, we simulate the laser fields dynamics in the periodic structures of different materials. We study how the dynamic ionization influences the field structure.

We analyze the dynamics of occupation probabilities for a certain type of design models by the use of two different methods. On the one hand we present some numerical calculations for two concrete interactions which point out that the occurrence of statistical dynamics depends on the interaction structure. Furthermore we show an analytical derivation for an infinite system that yields statistical behaviour for the average over the whole ensemble of interactions in the Van Hove-limit.

Experiments in the field of high energy physics make use of very complex detector systems. Extraction of meaningful results from these experiments needs a deep understanding of the detector performance. The most important tool in the process of understanding is the use of simulation of some known physics processes. Tools were being developed from late 1970s with more and more improved modeling of electromagnetic and strong interaction of particles with matter. These tools are also used to design a detector system of present day high energy physics experiment. Design and construction of detectors for the experiments at the Large Hadron Collider (Lhc) took nearly two decades. Detector simulation played an important role in these designs. One of the most important toolkits and its use in one of the experiments at the Lhc are described in this paper.