Program summer term 2019

 

Monday, April 15, 2019, 4:15pm, Hörsaal 28 D 001

Malte Göttsche (RWTH Aachen University)

Nuclear weapon control

Abstract:
Today, there exist over 14,000 nuclear weapons, and large weapons-usable fissile material stocks allowing the production of many more. To enable international agreements on warhead and fissile material reductions, a strong verification regime is essential. This requires both policy and physics research, as new verification concepts and techniques will be required. On the one hand, radiation detection techniques suited to establish the authenticity of nuclear warheads to be dismantled must be developed. On the other hand, new concepts are required to estimate the amount of produced weapons-usable fissile materials. This is the purpose of nuclear archaeology, which attempts to reconstruct the past fissile material production using measurements in shut-down nuclear facilities and extensive simulations.

Host:
Achim Stahl

 

Monday, April 29, 2019, 4:15pm, Hörsaal 28 D 001

Prof. Andreas Offenhäusser (FZ Jülich)

Mind the gap – design and characterization of the neuroelectronic interface

Abstract:
Nowadays, the best approach for longterm studies of the electrophysiological activity of neurons in vitro and in vivo is based on planar microelectrode arrays (MEA) or field-effect transistors (FET). These devices are also relevant for neuronal implants where they can restore lost sensory function, be part of a brain controlled machine interface or act as electronic alternatives to pharmaceuticals. However, the weak coupling between cell membrane and electrode surface is one of the major limiting factors and technology of 3D nanostructures for cell-chip coupling is currently a vivid field of investigation. Our present study focuses on the investigation of cell-chip interfaces with in various geometries, from planar structures to optimized 3D nanoelectrodes for extracellular recordings and stimulations.

Host:
Jörg Fitter

 

Monday, May 13, 2019, 4:15pm, Hörsaal 28 D 001

Prof. Thomas Zentgraf (University of Paderborn)

Holographic metasurfaces: A new route to information encryption and multiplexing

Abstract:
Optical components often rely on the refraction at geometrically shaped interfaces or spatial modulation of the phase during the propagation of light. Both effects, however, require a variation of the refractive index in three-dimensional space and lead to optical elements that are significantly thicker than the wavelength. New approaches with artificially structured materials along a surface, so-called metasurfaces, open exciting possibilities for the realization of compact optical elements. The flexibility in the design and manufacturing of optical metasurfaces allows to control the propagation of light to a high degree of freedom. Metasurfaces have the advantage that they can provide full control over light propagation with relatively low manufacturing costs and no requirements on complex three-dimensional nanofabrication techniques. The talk will provide an overview of the concept of geometric-phase metasurfaces and show recent developments in the field of beam shaping and holography.

Host:
Thomas Taubner

 

Monday, May 27, 2019, 4:15pm, Hörsaal 28 D 001

Prof. Licia Verde (University of Barcelona)

Post-precision cosmology

Abstract:
The standard cosmological model has been established  and its parameters are now measured with unprecedented precision. This model successfully describes observations from widely different epochs of
the Universe, from primordial nucleosynthesis all the way to the present day.

However, there is a big difference between modelling and understanding. The next decade will see the era of large surveys. A large coordinated effort of the scientific community in the field is on-going to map the cosmos; it will produce an exponentially growing amount of data. In the past, whenever  there was a major advance in observing the cosmos, cosmology has provided us with “surprises”,  and some had profound implications for physics. I will discuss what the next “surprise” from cosmology may be and its possible implications.

Host:
Philipp Mertsch

 

Monday, June 17, 2019, 4:15pm, Hörsaal 28 D 001

Prof. Klaus Kirch (Paul Scherrer Institute)

Low energy particle physics

Abstract:
Precision physics experiments at low energies test our understanding of the fundamental interactions and underlying symmetries. I will discuss examples of measurements with muons and neutrons tackling aspects of fundamental constants, interactions and symmetries. PSI is home to the strongest sources of low momentum pions, muons and ultracold neutrons. Positive muons and their decays determine the charged weak interaction and tightly constrain physics beyond the Standard Model (SM) of particle physics. With electrons, they form hydrogen-like muonium atoms allowing tests of QED and studying the gravitational interaction of antimatter. Negatively charged muons can replace electrons to form muonic atoms. They can be used to measure nuclear charge radii, e.g., of the proton and deuteron but essentially throughout the nuclear chart. Permanent electric dipole moments of neutrons or muons would violate time reversal symmetry and signal CP violation beyond the SM and are among the top priorities of fundamental particle physics.

Host:
Jörg Pretz