PD Dr. Johannes Bleibel
The research activities stretch across the fields of soft condensed matter, computational physics, and theoretical nuclear and particle physics. A common subject matter of these fields is the particle based simulation of many-body systems e.g. the Brownian dynamics of colloidal particles trapped at fluid interfaces under the influence of long-ranged capillary interactions.
The scientific work is mainly dedicated to soft matter physics, in particular to the dynamics of colloids trapped at fluid interfaces. Depending on the size of the colloids, these two-dimensional systems may exhibit long-ranged capillary interactions, which are caused by the deformation of the interface due to the colloidal particles and vary logarithmically with the distance. These systems have been studied in analogy to three dimensional Newtonian gravity. In particular the Jeans' instability and clustering phenomenology typically found in self gravitating systems has been investigated with the help of Brownian dynamics simulations and dynamical density functional theory (DDFT). As the range of the interaction can be varied, this system proved to be ideal to study the transition from self gravitating systems (long-ranged attractive interaction) towards the phenomenology of spinodal decomposition (short-ranged attraction). It emerged, that for intermediate ranges, a radially symmetric distribution collapses towards its center upon building up an inbound shock wave at the outer rim of the distribution. The inclusion of hydrodynamic interactions is currently under investigation, both, in Brownian dynamics and in comparison to lattice Boltzmann simulations. A rich spectrum of new and interesting results for further studies is expected to emerge.
Additionally the Monte-Carlo version of the Quark-Gluon String Model has been used to simulate collisions of protons for the Large Hadron Collider at CERN. For this purpose many of the parameters of the model have been updated in close collaboration with Prof. L.V. Bravina and E.E. Zabrodin of the University of Oslo. The simulations aim at the description and prediction of well known observables such as multiplicities, correlations and scaling behavior at LHC, in continuity to older results of the experiments Tevatron (Fermilab) and SPS at CERN.