Physikalisches Kolloquium

The mystery of the S-star cluster orbiting the supermassive black hole in the center of the Milky Way

The Galactic center hosts one of the most mysterious structures of the Milky Way, the S-star cluster. This spheroidal ensemble of young, massive stars with coeval ages of 1 million years is confined to a region of less than 0.1 light years from Sgr A* which marks the very center of the Milky Way. Their highly eccentric orbits have been reconstructed with ultra high precision, demonstrating that they orbit a supermassive black hole with a mass of 4.297 million solar masses right at the position of Sgr A*. In 2020, this discovery was awarded the Nobel Prize in Physics. The origin of the S-star cluster is puzzling as single stars typically condense out of molecular clouds with radii much larger than the whole cluster. In addition, no star is expected to form within the enormous tidal field and hostile environment of the central supermassive black hole. Currently, the S-stars are embedded in a million degress hot diffuse gas bubble, which again is not a favorite condition for star formation. How did this cluster with its extreme properties form? And how is its formation related to the origin and growth of supermassive black holes that are now found in the centers of many galaxies? I will summarize recent research results and discuss open questions.

Under Pressure: Uniaxial Stress as a Probe of Quantum Materials

The electronic, magnetic, and mechanical properties of solids are intimately connected to the arrangement of the constituent atoms. The ability to directly tune the spacing between atoms – that is, to impose a controlled strain – therefore represents a powerful way of manipulating solids at a fundamental level. With methods pioneered over the past decade that employ piezoelectric actuators to supply forces at low temperatures, elastic tuning, in which one manipulates a crystal by tensioning or compressing it, has become a powerful tool in the study of quantum materials. In my talk, I will describe how we use these methods to both modify and measure the complex and sometimes counterintuitive properties that emerge in solids at low temperatures.

Local host: Prof. Dr. Cornelius Krellner

Hilary Noad, Ph.D., ist Preisträgerin der Wilhelm-Heraeus-Stiftungsgastprofessur 2025. Weitere Informationen zur Stiftungsgastprofessur finden Sie hier.

!!! ACHTUNG: Vortrag findet im H2 des Otto-Stern-Zentrums statt !!!

A Journey into the Dark Universe: Gravitational Waves as New Probes of Dark Matter

Gravitational waves have opened an unprecedented window into the universe. They not only allow us to test gravity under extreme conditions, but also provide a powerful new tool to explore one of the most profound mysteries of the universe: the nature of dark matter. 

In my talk, I will take you on a journey into the dark universe. I will show how we can use the full gravitational wave spectrum — from the high frequencies accessible to the Laser Interferometer Gravitational-Wave Observatory (LIGO), to the intermediate band to be probed by the Laser Interferometer Space Antenna (LISA), down to the low frequencies targeted by pulsar timing arrays such as NANOGrav — to place new constraints on the particle nature of dark matter. 

Through these examples, I will illustrate why now is such an exciting time for research in the rapidly evolving field of gravitational wave physics.

Local host: Prof. Dr. Owe Philipsen

Physicists in banking supervision: just another job in finance or a perfect match?

Have you ever considered working for a central bank? No? Well, neither did I while I was studying Physics and working on my PhD. And yet, here I am! In this session of "Physiker*innen im Beruf", I will share how I ended up at Deutsche Bundesbank and how I managed the transition from academia to the public sector. We will talk about the basics of risk modelling and build a simple risk model together, we will discuss the setup of banking supervision in Germany and Europe, and what that entails for my day-to-day job as an on-site banking supervisor. So please join the Gleichstellungsrat and me on 2 July to see what a physicist works on in on-site banking supervision for Deutsche Bundesbank.

Local host: Gleichstellungsrat Physik

Job Opportunities during FAIR installation and beyond

Have you ever considered working for a research center right around Frankfurt's corner? In this session of Physiker*innen im Beruf, we will share two individual career pathways into science management and a project-leadership role. We will talk about how we have experienced the transition from academia to our current management responsibility. We will briefly keep you updated on the FAIR project realization, current challenges during installation and commissioning and how we contribute in our day-today job. We will provide some insight to current and upcoming job offers at our center and will get you in touch with the decision makers of your departments and fields of interest. 

Local host: Prof. Dr. Marc Wagner

Herausforderungen eines Übertragungsnetzbetreibers – in der Physik und in der Regulatorik

„Das ist jetzt Physik“  ist einer der Sätze, der im Arbeitsalltag bei einem Netzbetreiber häufig fällt. Das ist häufig als Gegenteil zu „Das ist Markt“ gemeint. Netzbetreiber sind an der Schnittstelle dieser beiden Welten dafür verantwortlich, dass Markt und Physik (und damit meinen wir dann eigentlich „Netz“) miteinander so funktionieren, dass auch weiterhin Strom „einfach aus der Steckdose“ kommt.

Aber was ist das Problem an Dunkelflauten und Hellbrisen? Und wie werden wir auch weiterhin in diesen speziellen Phasen unser Netz sicher betreiben? Hilft uns der „Batterie-Tsunami“, der aktuellen Meldungen zufolge bereits bis zu tausend Gigawatt Batterien ans Netz bringen soll?

Local host: Prof. Dr. Horst Schmidt-Böcking

Project Ethel: Using AI for Teaching and Learning at ETH Zurich

Large language models have moved from generating amusing fiction to outperforming undergraduates on first-year physics and chemistry exams, forcing us to rethink how knowledge is produced, assessed, and learned. Drawing on a series of empirical studies - from GPT-3.5 barely passing an introductory physics course to GPT-5 solving a multi-page general chemistry final more accurately and faster than any student - I explore what these systems can and cannot yet do, and how this reshapes our notions of expertise and academic integrity. I then introduce “Ethel,” ETH Zurich’s on-premises AI ecosystem that uses commercial LLMs through controlled workflows to support course-specific chatbots, accessibility services, automated feedback, and large-scale grading assistance with psychometric, human-in-the-loop safeguards. 

Rather than treating AI as a better teacher or as a prohibition problem, the talk discusses how institutions can curate AI for students, design assessments that focus on reasoning processes instead of answers, and maintain transparency and student agency in high-stakes settings — without forgetting that our students are humans navigating yet another disruptive technological wave.

Local host: Prof. Dr. Thomas Wilhelm

Quantum Materials: a new paradigm for sensing

Quantum materials provide responses and states of matter with no classical analogs. As such, they offer opportunities to create various platforms for future devices crucial to human health, energy efficiency, communications, and imaging. I will describe the physics challenges and sensing opportunities these materials offer. I will then focus on using the relativistic electrons in graphene for biosensing. Specifically, we have developed a new platform for multiplexed, rapid, easy-to-use detectors of biological analytes. I will discuss the unique aspects of graphene involved, resulting in our demonstration of a handheld device that detects antibiotic-resistant bacteria, decease biomarkers, opioids, and respiratory infections in saliva and wastewater at concentrations an order of magnitude better than mass-spectroscopy. Time permitting, I will briefly mention other efforts in our group to study novel quasi-particles in these systems.

Local host: Prof. Dr. Roser Valentí

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Exotic Hadrons and Where to Find Them

The quantum field theory of strong interactions describes strongly interacting particles (hadrons) as composites of fermions with a colour charge (quarks) and coloured mediator bosons (gluons).

For a long time, every known hadron could be explained either as a meson made of a quark-antiquark pair or as a baryon made of three quarks. But since 2003, dozens of exotic heavy hadrons have been discovered which do not fit into the conventional description, revealing a poorly understood aspect of the strong nuclear force.

In this colloquium, I will discuss the exotic heavy-hadron puzzle that has challenged hadron physicists for more than two decades. I will then describe exciting recent developments through which a unified picture of the exotic heavy hadrons is finally emerging.

Local host: Prof. Dr. Marc Wagner