A fundamental property that a planet can have is if it is encompassed by radiation belts of highly energetic electrons and ions approaching light speed. The radiation belts of Jupiter and Saturn differ from Earth’s Van Allen belts not only in their extent and intensity but also in the physical processes governing them. We will explain the physics of giant planet radiation belts based on data from space missions as Juno and Cassini, and show examples of recent and ongoing studies.
Self-interacting dark matter (SIDM) has been proposed as a possible
solution to the long-standing small-scale structure problems encountered in the collisionless cold DM paradigm. I will discuss to what extent particle physics models can provide the required self-interaction cross section, while still being consistent
with other astrophysical and laboratory searches for dark matter. In
particular, I will discuss the role of complementary constraints on such models from direct detection, the Cosmic Microwave Background and Big Bang Nucleosynthesis.
Das Institut für Astrophysik bietet in unregelmäßigen Abständen öffentliche Führungen mit Beobachtungsmöglichkeit am 50-cm-Spiegelteleskop an. Während der Führungen werden die Forschungs- und Ausbildungseinrichtungen des Instituts vorgestellt und, bei klarem Himmel, eindrucksvolle Himmelsobjekte (z. B. Mond, Planeten, Gasnebel, Sternhaufen, Galaxien) im Fernrohr gezeigt. Die Führungen werden durch eine halbstündige Präsentation zu einem aktuellen Thema aus der astronomischen Forschung ergänzt.
In spite of its technological relevance in the energy conversion and storage, our knowledge about the microscopic structure of electrochemical electrode-electrolyte interfaces and electrical double layers is still rather limited. The theoretical description of these interfaces from first principles is hampered by three facts. i) In electrochemistry, structures and properties of the electrode- electrolyte interfaces are governed by the electrode potential which adds considerable complexity to the theoretical treatment since charged surfaces have to be considered. ii) The theoretical treatment of processes at solid-liquid interfaces includes a proper description of the liquid which requires to determine free energies instead of just total energies. This means that computationally expensive statistical averages have to be performed. iii) Electronic structure methods based on density functional theory (DFT) combine numerical efficiency with a satisfactory accuracy. However, there are severe shortcomings of the DFT description of liquids, in particular water, using current functionals.
Despite these obstacles, there has already significant progress been made in the first-principles modeling of electrochemical electrode-electrolyte interfaces. In this contribution, I will present our attempts to contribute to this progress by systematically increasing the complexity of the considered systems . Different approaches to describe aqueous electrolytes at electrodes using first-principles calculations will be compared: the electrolyte can be described either as a thermodynamic reservoir or using implicit of explicit solvent models [2,3]. The equilibrium coverage of specifically adsorbed anions such as halides will be addressed which is an integral part of the realistic modeling of electrochemical double layers . Furthermore, the modelling of electrocatalytic reactions occurring in fuel cells [3, 4] will be presented. Finally, first attempts to model structures and processes in batteries using electronic structure calculations will be presented.
Charge-state investigations of single adsorbates on ultrathin insulating films have revealed fundamental charging properties. For example, charge-state determination and control of adatoms (1) and molecules on bilayer NaCl as well as the charge-distribution mapping within a molecule was demonstrated. However, multilayered insulating films are necessary to efficiently confine charges at the surface - requiring better understanding of adsorbates charging and their quantification on thicker films.
Here, we exhibit the essential steps towards exploring stable charge states of single molecules. First, we demonstrate reversible charge-state manipulation, leading to a tip-induced lateral single-electron transfer between molecules. Second, we present a novel approach based on single-electron detection using an atomic force microscope that allows tunneling spectroscopy measurements of a single molecule on an insulator. This culminates in the characterization of a fundamental property of the molecule/surrounding system, the reorganization energy.
The double focusing mass spectrometer (DFMS) of the
ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis)
instrument on board Rosetta has enabled the discovery of a zoo of
neutral constituents in the coma of comet 67P/Churyumov-Gerasimenko.
This talk will focus on halogen-bearing species in the coma and
address their abundances, variability and isotopic composition.
Thermoelectric materials are a very interesting topic of actual research due to their capability of converting heat into electricity without any moving parts and without the need of huge temperature gradients. A very promising and already used material is Sb2Te3. For further understanding the structure property relations in this material and optimizing its thermoelectric properties, epitaxial thin films have been synthesized by PVD and studied in the FEI TITAN ETEM. Thermal conductivity measurements have been made using the 3omega method. Furthermore, the Kapitza resistance of various involved interfaces has been determined, allowing for high precision determination of the film thermal conductivity. The analysis shows that the nearly single crystalline films show a remarkably small cross plane (c-axis) thermal conductivity pointing to an intrinsic limitation by the layered structure.
The theory of causal fermion systems is a recent approach to describe fundamental physics. Giving quantum mechanics, general relativity and quantum field theory as limiting cases, it is a candidate for a unified physical theory. The dynamics is described by a novel variational principle, the so-called causal action principle. From the mathematical perspective, causal fermion systems provide a general framework for describing and analyzing non-smooth geometries. In the talk I will introduce the mathematical setting and explain the connection to quantum field theory.
I will discuss the ongoing experiments: Cosmic Axion Spin-Precession experiment (CASPEr) and the Global Network of Optical Magnetometers for Exotic physics searches (GNOME) searching for ultralight galactic dark matter using magnetic-resonance techniques and new approaches to measuring parity violation in chiral molecular systems. I will also talk about nuclear magnetic resonance (NMR) at zero and ultralow magnetic field (a.k.a. NMR without magnets).
Solar-like and low-mass stars (M < 1.3 Msun) undergo a significant rotational evolution, by 1-2 orders of magnitude in terms of surface rotation period, controlled by three main mechanisms: 1) structural changes, affecting the stellar radius and moment of inertia; 2) angular momentum loss at the surface, through a magnetized stellar wind; 3) angular momentum redistribution in the interior. The details of the wind braking phenomenon, and even the physical nature of the internal rotational coupling, are currently controversial.
The early main sequence spin-down, as probed by the color-period diagrams of well-studied open clusters, is characterized by the gradual emergence of a "slow-rotators sequence", possibly the manifestation of a fundamental transition occurring in the star between different magnetic configuration/dynamo regimes. The observed properties of the slow-rotators sequence provide valuable insight into the wind braking and internal coupling mechanisms, such as their dependence on stellar structural and rotational parameters.
The internal rotation profile of late main sequence and post-main sequence solar-type stars can be probed using asteroseismology. These observational constraints show that by solar age a nearly solid-body rotation state is attained; radial differential rotation subsequently develops in the subgiant phase, but decreases once more during the red giant branch ascent. A rotational coupling mechanism whose efficiency is constant in time is manifestly incompatible with this behavior, while models incorporating the effects of the turbulent viscosity generated by MHD instabilities are in good agreement with the observations.
Highly filled particulate nanocomposite films consisting of metal nanoparticles in a dielectric organic or ceramic matrix have
unique functional properties with hosts of applications. In most applications, a high filling factor close to the percolation
threshold with control of the particle separation on the nm scale is essential because the functional properties often require
short range interaction between nanoparticles. The present talk demonstrates how vapor phase deposition techniques can be
employed for tailoring the nanostructure and the resulting properties. Vapor phase deposition, inter alia, allows excellent
control of the metallic filling factor and its depth profile as well as the incorporation of alloy nanoparticles with well-defined
composition. We applied various methods such as sputtering, evaporation, and plasma polymerization for the deposition of
the matrix component, while the metallic components were mostly sputter-deposited or evaporated. Moreover, a high-rate gas
aggregation cluster source was utilized to obtain independent control of filling factor and size of the embedded nanoparticles.
Examples include optical composites with tuned particle surface plasmon resonances for plasmonic applications [ 1],
magnetic high frequency materials with cut-off frequencies well above 1 GHz , sensors and photoswitchable devices 
that are based on the huge change in the electronic properties near the percolation threshold, and biocompatible antibacteria l
coatings with tailored release rate . In addition to the particulate composites, a new concept of layered magnetoelectric
composites will be presented for robust, fully integrable, broad band magnetic field sensors based on the delta E effect .
 M. Keshavarz Hedayati, M. Javaherirahim, B. Mozooni, R. Abdelaziz, A. Tavassolizadeh, V.S.K. Chakravadhanula, V.
Zaporojtchenko, T. Strunskus, F. Faupel, M. Elbahri, Design of a perfect black absorber at visible frequencies using
plasmonic materials, Adv. Mater. 23 (2011) 5410.
 H. Greve, C. Pochstein, H. Takele, V. Zaporojtchenko, F. Faupel, A. Gerber, M. Frommberger, E. Quandt,
Nanostructured magnetic Fe-Ni-Co/Teflon multilayers for high frequency applications in the gigahertz range, Appl. Phys.
Lett. 89 (2006) 242501.
 S.W. Basuki, V. Schneider, T. Strunkus, M. Elbahri, F. Faupel, Light-Controlled Conductance Switching in Azobenzene-
Containing MWCNT–Polymer Nanocomposites, ACS Appl. Mater. Interfaces 7 (2015