Kolloquien

We celebrate a decade of gravitational wave astronomy. One of the most remarkable achievements concerns tests of General Relativity and of the nature of compact objects. Gravitational collapse in Einstein’s theory leads to black holes, leaving behind a geometry with light rings, ergoregions and horizons. These peculiarities are responsible for uniqueness properties and energy extraction mechanisms that turn black holes into ideal laboratories of strong gravity, of particle physics (yes!) and of possible quantum-gravity effects. I will review some of the things we learned during the last ten years.   more...

Ion beam therapy has emerged as a highly precise form of radiation treatment, exploiting the physical and biological advantages of protons and heavier ions. Its characteristic Bragg peak enables superior dose conformity compared to conventional photon therapy.   more...

Polymers, long chain molecules, comprise important materials of our daily life, being it simple commodities with all their advantages and disadvantages or high-tech materials in electronics or medicine, to give just two examples. Furthermore, biopolymers such as cellulose or proteins are central functional constituents of living organisms. Not surprisingly, they have been subject of applied physics research since their discovery/invention.   more...

While the phenomenon of cosmic expansion is well-established, it is also possible that this expansion could engender a process of cosmic condensation. Indeed, in the presence of new physics beyond the Standard Model, the early universe could have undergone a change of state in a manner analogous to the condensation of water vapor into liquid.   more...

Photonic Time Crystals (PTCs) are dielectric media whose refractive index is strongly modulated periodically in time at time scales shorter than a single optical cycle. These systems conserve momentum but not energy, and are characterized by momentum bands and bandgaps where the amplitudes of their eigenmodes can increase or decrease exponentially.   more...

To understand galaxies, we must understand the physical processes and local conditions that drive their buildup of stellar mass through star formation. This evolution is regulated through the baryon cycle, the transformation of gas into stars and eventual ejection and recycling of that material to form the next generation of stars.   more...

The neutron is a key building block of ordinary matter, more than half of the Earth's mass is contributed by neutrons, but when freed from the confines of a stable atom a neutron decays into a proton, an electron, and an antineutrino with a lifetime of about 15 minutes. Free neutron decay is the prototype semileptonic weak interaction and simplest nuclear beta decay. There are no complications from nuclear structure, and the decay energy is small compared to the nucleon mass so recoil-order corrections enter below the 0.1% level, so neutron decay is an attractive system for precise low energy weak interaction measurements.   more...