Scientific Interests

Cosmology in a petri dish?

Interfacially trapped, micrometer-sized colloidal particles interact via long-ranged capillary attraction which is analogous to two-dimensional screened Newtonian gravity with the capillary length λ as the screening length. Using Brownian dynamics simulations, density functional theory, and analytical perturbation theory, we study the collapse of a finitely-sized patch of colloids. Whereas the limit λ → infinity corresponds to the global collapse of a self-gravitating fluid, for intermediate λ we predict theoretically and observe in simulations a ringlike density peak at the outer rim of the disclike patch, moving as an inbound shock wave. For smaller λ the dynamics crosses over to spinodal decomposition showing a coarsening of regions of enhanced density which emerge from initial fluctuations. Experimental realizations of this crossover scenario appear to be well possible for colloids trapped at water interfaces and having a radius of around 10 micrometer.

Crystallization in colloidal systems

Hard spheres or hard sphere--like colloids are model system to study crystal properties and nucleation kinetics on micrometer scales. We develop and employ very precise density functional methods (Fundamental Measure Theory) to dscribe these systems and study the relation of effective models such as Phase Field Crystal to this precise density functional description. This work is supported by the DFG Priority Programm SPP 1296 Heterogeneous Nucleation (2009-).

Particles at soft interfaces

The effective interactions between trapped colloidal particles at interfaces was the research focus of the Junior Research Group 2006-2012. More information on the research can be found in the report to the DFG.

QCD phenomenology: covariant baryon models

The description of baryons as relativistic bound states of quark and diquark contains all basic properties of QCD: relativistic covariance, confinement and spontaneous breaking of chiral symmetry. In this approach, the complex and more or less unknown quark-quark correlations are replaced by the notion of diquarks as "quasi"particles. Binding with a third quark is effected by attractive quark exchange which is the minimal interaction to restore the Pauli principle of a three-quark state. A basic exposition of the model with some applications can be found in my PhD thesis, available at nucl-th/0012067 .