Department for Physics and Astronomy

Events

Physikalisches Kolloquium

Friday, 30. October 2026 5:00 pm Simulating the Universe

Dr. Dylan Nelson, Institute for Theoretical Astrophysics, Center for Astrophysics (ITA/ZAH), Heidelberg University, Germany. Simulating the Universe Dr. Dylan Nelson Institute for Theoretical Astrophysics, Center for Astrophysics (ITA/ZAH), Heidelberg University, Germany It has recently become possible to numerically simulate large, representative volumes of the Universe. These cosmological (magneto)hydrodynamical simulations solve for the coupled evolution of gas, dark matter, stars, and supermassive black holes interacting via the coupled equations of self-gravity and fluid dynamics, all within the context of an expanding spacetime. The IllustrisTNG simulations exemplify the current state-of-the-art in this context (www.tng-project.org). They simultaneously resolve tens of thousands of individual galaxies, enabling a variety of studies on galaxy formation and evolution, as well as large-scale structure and cosmology. I will give a tour of the TNG simulations, touching on some favorite scientific insights. I will conclude with a look towards the future: "star-by-star" simulations of high-redshift galaxies during the first billion years of cosmic time.

Particle Colloquium

HGCAL at CMS and AI calibration models

Dr. Katya Krüger, DESY Hamburg

Astronomy colloquium

Tuesday, 3. November 2026 4:30 pm Decoding Galaxies & Star Formation Feedback with 100,000 Star Clusters: PHANGS-HST & JWST today, the future with HWO

Janice Lee , StSci The PHANGS-HST and JWST Treasury Programs have produced the most extensive inventories to date of optically visible and dust-obscured star clusters across nearby galaxies. A coherent picture is emerging of the earliest phases of star formation, built from complementary studies that consistently point to short dust-clearing timescales (~3 Myr), in agreement with earlier optical studies. Together, these results underscore the central role of early, pre-supernova feedback in regulating the star formation cycle. Drawing on the statistical power of tens of thousands of clusters spanning dozens of galaxies, I will synthesize what PHANGS and related programs have revealed about cluster evolution, feedback, and the use of clusters as “clocks” for timing key phases of star formation. Looking ahead, I will highlight work on the Habitable Worlds Observatory, NASA’s next flagship astrophysics mission after Roman, which will operate as a true “Super-Hubble,” with UV–optical capabilities to transform our understanding of star formation and fields across astrophysics. To arrange a visit with the speaker during the visit, please contact their host: Ralf Klessen

Center for Quantum Dynamics Colloquium

Wednesday, 4. November 2026 4:30 pm Spin-Orbit-Coupled Bose-Einstein Condensates: From Supersolidity to the Hofstadter Butterfly

Prof. Dr. Leticia Tarruell, ICFO – The Institute of Photonic Sciences, Spain Quantum liquid droplets in a mixture of Bose-Einstein condensates Leticia Tarruell ICFO-The Institute of Photonic Sciences, Castelldefels (Barcelona), Spain Self-bound states appear in contexts as diverse as solitary waves in channels, optical solitons in non-linear media and liquid droplets. Their binding results from a balance between attractive forces, which tend to make the system collapse, and repulsive ones, which stabilize it to a finite size. This talk will present our recent experiments on dilute quantum liquid droplets: macroscopic clusters of ultra-cold atoms that are eight orders of magnitude more dilute than liquid Helium, but have similar liquid-like properties. In particular, they remain self-trapped in the absence of external confinement due to the compensation of attractive mean-field forces and an effective repulsion stemming from quantum fluctuations [D. S. Petrov, Phys. Rev. Lett. 115, 155302 (2015)].. We observe these self-bound droplets in a mixture of two Bose-Einstein condensates with attractive inter-state and repulsive intra-state interactions. Exploiting in situ imaging, we directly measure their ultra-low densities and micro-meter scaled sizes, and demonstrate the many-body origin of their stabilization mechanism. Furthermore, we observe that for small atom numbers quantum pressure is sufficient to dissociate the droplets and drive a liquid-to-gas transition, which we map out as a function of atom number and interaction strength [C. R. Cabrera et al., arXiv:1708.07806].. In a second series of experiments, we study the difference existing between these liquid droplets and more conventional bright solitons. In analogy to non-linear optics, the former can be seen as one-dimensional matter-wave solitons stabilized by dispersion, whereas the latter correspond to high-dimensional solitons stabilized by a higher order non-linearity due to quantum fluctuations. We find that depending on the system parameters, solitons and droplets can be smoothly connected or remain distinct states coexisting only in a bi-stable region, and we determine experimentally its boundary [P. Cheiney et al., arXiv:1710.11079].

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