Kolloquien

The four fundamental interactions and their symmetries, along with the fundamental constants and properties of elementary particles - such as masses and magnetic moments - form the foundational structure of the universe and underpin the well-tested Standard Model (SM) of particle physics. Conducting stringent tests of these interactions and symmetries under extreme conditions, at low energies and with the highest precision, for example by comparing particles and their counterparts, the antiparticles, allows us to probe for potential physics beyond the SM. Advancing these tests beyond their current limits requires the development of innovative experimental techniques.   more...

Aerosols are small airborne particles that are surrounding us but are mostly invisible to our eyes. Multiple natural and anthropogenic emission sources lead to various chemical compositions of aerosols in the Earth's atmosphere. Influences of aerosols on radiative transfer and cloud microphysical processes are qualitatively understood, but the magnitudes of these effects are under debate with important implication for understanding past and future climate change. In this colloquium, I will give a glimpse on aerosol effects on climate, explain some reasons for uncertainties in our understanding of their effects on climate, and outline how we can make progress despite persistent model uncertainty.   more...

Gravity remains, to date, the most mysterious of the four known fundamental interactions. The quest for a consistent theory of quantum gravity is believed to be deeply intertwined with some of the most pressing outstanding open questions in high energy physics and cosmology. In this colloquium we will review some recent proposals for universal constraints which every effective field theory must obey if it arises as the low-energy limit of a consistent quantum gravity theory. A particularly fruitful point of departure is the study of quantum gravity theories near asymptotic weak coupling.   more...

Most of the rain we experience forms not as liquid water, but as ice. In mid-latitude clouds, ice formation is a prerequisite for precipitation, but at temperatures warmer than -36?^oC, water droplets can only freeze heterogeneously with the help of particles called ice-nucleating particles (INPs). These INPs are very rare among atmospheric aerosols, and we still don’t fully understand what makes one particle a more effective INP than another.   more...

The stable generation of high-temperature and low-density hydrogen plasmas (ion and electron temperature in the range 10-20 keV resp. 100-200 million degree Kelvin) is the basis for the use of nuclear fusion to generate heat and electric power. The most promising path is to use strong, toroidally shaped, twisted magnetic fields to confine the electrically charged plasma particles in order to avoid heat losses to the cold, solid wall elements.   more...

The presence of massive black holes in the first galaxies has been predicted theoretically for many years. Until the launch of the space telescope JWST the bulk of observational data hinged on very bright sources 'luminous quasars' detected about one billion years after the Big Bang. Now a large number of fainter sources, candidate active massive black holes, have been identified, some at much earlier cosmic times.   more...

Some of the most fascinating phenomena in nature arise when electrons behave as quantum mechanical waves that interact with one another. But how can we visualize these electronic waves in action?   more...

The field of AI & Music has come a long way, from early attempts at algorithmic composition to a wide variety of intelligent sound and music technologies that are shaping today's digital music world. As in many other application domains, many of the recent successes are based on exploiting and adapting the latest advances in statistical machine learning, transferring them from fields like computer vision and language processing.   more...

Recent observations have revealed a surprising diversity in planetary systems, but the processes that shape them are still not fully understood. Key questions remain about how and when planets form, how they interact with their surrounding environment - the protoplanetary disk, birthplace of planets - and how these interactions affect both the planets and the disk.   more...