Freitag, 4. Juli 2025 17:00 Uhr  Generative Neural Networks for the Sciences

Prof. Dr. Ullrich Köthe, Interdisciplinary Center for Scientific Computing (IWR), Heidelberg

Generative modelling with normalizing flows has worked well in scientific applications like simulation-based inference. However, the peculiar design makes it difficult to incorporate prior knowledge (such as laws of physics or chemistry) into their architecture. Free-form flows eliminate this restriction by means of a new training algorithm. Manifold free-form flows elegantly exploit these opportunities in the case when we know that the data reside on a manifold. The talk will explain the underlying theory and present experimental evidence for the promising behavior of the new approach.

Highlights of the HL-LHC physics projections by ATLAS and CMS

Prof. Dr. Pamela Ferrari, CERN

Dienstag, 8. Juli 2025 16:30 Uhr  Compact star mergers, kilonovae and r-process element production

Stephen Smartt , University of Oxford Two binary neutron star mergers have been detected from their gravitational wave signature. The first, in 2017 had an electromagnetic counterpart comprising a high energy and radio emission and a thermal component called a kilonova powered by radioactive heavy elements. The composition of the ejecta, mostly elements heavier than iron is still debated. Nucleosynthesis and atomic data arguments suggest a number of 1st and 2nd process elements have detected spectral signatures. The was no counterpart from the second binary neutron star merger in 2019 and no further merger has been detected by LIGO-Virgo-Kagra since. However, surprisingly two long gamma ray bursts have shown convincing signatures of an infra-red excess powered by heavy element decay, and the luminosity can be modelled with kilonova thermal emission. I will present the data, current debates on the chemical element signatures in the spectrum, discuss the relatively low rate of discovery and the put the two long GRB discoveries into context. To arrange a visit with the speaker during the visit, please contact their host: Fabian Schneider

Mittwoch, 9. Juli 2025 17:00 Uhr  Exploring quantum Hall physics with ultracold dysprosium atoms

Prof. Sylvain Nascimbene, Département de Physique, École normale superérieure, Paris Exploring quantum Hall physics with ultracold dysprosium atoms Prof. Sylvain Nascimbène Laboratoire Kastler Brossel, Collège de France, Paris Ultracold atomic gases offer a versatile platform for exploring rich phenomena in quantum matter. In particular, topological states akin to those found in the quantum Hall effect can be engineered by simulating orbital magnetic fields—an approach greatly facilitated by the use of synthetic dimensions. In this talk, I will present our experimental realization of a quantum Hall system using ultracold gases of dysprosium atoms. By leveraging the atom’s large internal spin (J=8), we encode a synthetic dimension and couple it to atomic motion via two-photon optical transitions, which generates an effective magnetic field. We observe hallmark signatures of quantum Hall physics, including a quantized Hall response and gapless, chiral edge modes. I will then describe a more intricate experiment designed to probe spatial entanglement by simulating the so-called entanglement Hamiltonian. Using the Bisognano-Wichmann theorem—which relates the entanglement Hamiltonian to a spatially deformed version of the original system—we implement this deformation along the synthetic dimension. Lastly, I will discuss our recent investigation into a topological phase transition, induced by introducing an additional lattice potential. I will highlight the system’s behavior in the critical regime and explore the emergent features associated with the transition.