Kolloquien

Microorganisms can move in complex media, respond to the environment and self-organize. The field of nano- and microrobotics takes inspiration from nature and strives to achieve these functions in synthetic systems. However, building synthetic motors and machines ‘bottom up’ such that they can mimic biological matter and function autonomously or such that they can be controlled externally, is challenging.   more...

Cosmic Rays with energies beyond 10²⁰ eV are regularly observed by the Pierre Auger Observatory covering an area of 3000 km². They are known to be of extragalactic origin but despite enormous progress being made in recent years, Nature has not fully revealed their sources, yet. However, a simultaneous description of the observed energy spectrum, mass composition and arrival directions suggests powerful nearby Starburst Galaxies as a key contributor -- an observation that is independently supported by multi-messenger observations involving high energy photons and neutrinos. The enormous particle energies arriving at Earth can also be used to probe new particle and fundamental physics and a few examples will be presented.   more...

The search for new quantum materials with novel properties is often focused on materials containing transition-metal, rare-earth and/or actinide elements. The presence of the atomic-like d or f orbitals provides a fruitful playground to generate novel phenomena. The intricate interplay of band formation with the local electron correlation and atomic multiplet effects leads to phases that are nearly iso-energetic, making materials’ properties highly tunable by doping, temperature, pressure or magnetic field. Understanding the behavior of the d and f electrons is essential for designing and controlling novel quantum materials. Therefore, identifying the d or f orbitals that actively participate in the formation of the ground state is crucial. So far, these orbitals have mostly been deduced from optical, X- ray and neutron spectroscopies in which spectra must be analyzed using theory or modelling. This, however, is also a challenge in and of itself, since ab-initio calculations hit their limits due to the many-body nature of the problem.   more...

Emissions from the world's data centers exceed those from air travel. Even when renewable energy sources are used, a lot of waste heat is generated that heats up the environment. Consequently, energy efficiency is of paramount importance. There are three main areas of energy efficiency or Green IT: data center efficiency, computer architecture efficiency, and last but not least, algorithm efficiency.   more...

The James Webb Space Telescope was launched on Dec. 25, 2021, and commissioning was completed in early July 2022. With its 6.5 m golden eye, and cameras and spectrometers covering 0.6 to 28 µm, Webb is already producing magnificent images of galaxies, active galactic nuclei, star-forming regions, and planets. Scientists are hunting for some of the first objects that formed after the Big Bang, the first black holes (primordial or formed in galaxies), and beginning to observe the growth of galaxies, the formation of stars and planetary systems, individual exoplanets through coronography and transit spectroscopy, and all objects in the Solar System from Mars on out.   more...

The number of gravitational-wave detections approaches the 100 mark and starts revealing the big picture of binary black hole populations. Several detected black holes have mass in the lower (2-5 Msun) or upper (~60-120 Msun) mass gap, challenging models of stellar and binary evolution. Furthermore, evidence for unequal-mass systems and non-negligible spin misalignment advocate for unconventional scenarios of binary black hole formation. We recently proposed that the mass function of the LIGO-Virgo black holes evolves with redshift.   more...

A great deal of interest has recently arisen in high-precision atomic physics experiments aimed at searching for New Physics beyond the Standard Model. These experiments became feasible due to outstanding achievements in the field of quantum control of matter and light.   more...

Living cells and their environments are examples of highly dynamic matter. For example, intracellular transport is based on diffusion, but also on active transport by molecular motors. Furthermore, the structure of a cell, its chemical content and also its mechanical properties can adapt at the timescale of seconds to minutes to external stimuli. Living cells also dynamically shape their extracellular surroundings. Hence, cells can be regarded as perfect examples of active, dynamic matter and can provide inspiration for shaping novel materials.   more...

Jeder kennt James Bond, den smarten Geheimagenten, der von Q mit kleinen Gadgets versorgt wird, um seine Abenteuer zu bestehen. Doch wie viel Realität steckt hinter den Erfindungen von Tüftler Q? Funktionieren die Uhren von 007 wirklich? Wie schafft es Bond immer wieder, tödliche Situationen zu überleben? Kann sich ein Auto wirklich sieben Mal überschlagen? Muss James Bond Physiker sein, damit er seine waghalsigen Stunts überlebt?   more...