Robert Weis

The Kirchhoff Institute for Physics (KIP) is named after a prominent physicist of the 19th Century: **Gustav Robert Kirchhoff**, who worked in Heidelberg for 21 years. His well-known lectures on experimental and theoretical physics attracted many students. Kirchhoff's ground-breaking research was extraordinarily diverse, spanning electrical, magnetic, optical, elastic, hydrodynamic and thermal processes. His laws for electrical circuits are well-known. At the time he was in Heidelberg, in conjunction with Robert Wilhelm Bunsen, he discovered spectral analysis and its application to solar radiation. In this way, Kirchhoff laid the foundation for modern astrophysics, as well as formulating the laws of thermal radiation, which played a key role in the discovery of quantum physics. The KIP aims to continue in this tradition of diverse scientific research and education.

Free spirit. Pioneer. Visionary: Gustav Kirchhoff's scientific findings are still of great importance today for many current research topics. As the founder of spectral analysis in the 19th century, the outstanding physicist (1824 to 1887) not only paved the way for modern astrophysics, but also environmental physics, modern atomic and molecular physics, chemistry and quantum physics still use spectroscopy today. And without Kirchhoff's rules for electrical networks, chip development and the analysis of electrical circuits would be inconceivable.

The Ruperto Carola lecture series in the summer semester 2024 on the occasion of the 200th birthday of Gustav Kirchhoff, who researched and taught as a professor at Heidelberg University for more than 20 years, provides - in addition to a historical introduction to Kirchhoff's life and work - insights into areas of modern research on which Kirchhoff's work has had an influence to this day.

* Dr. Eva Schinnerer , Max-Planck-Institut für Astronomie, Heidelberg,
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Star formation is a vital process for stellar mass growth during the evolution of
galaxies. Our understanding of where stars form and how their formation is regulated
across galactic disks is surprisingly incomplete. In order to resolve the sites of recent
(or future) star formation and sample the time evolution of the star formation process,
high spatial resolution observations of nearby galaxies are required that reach the
scales of the star-forming units, namely giant molecular clouds and HII regions.
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Next CQD Colloquium (funded by Structures) will be given by Prof. Quentin Glorieux

**Please note the place and time: Wednesday, 26 ^{th} of June at 4:30 p.m., PI, INF 226, K 1-3, Goldenbox**

The main talk will be given by Prof. Quentin Glorieux about:

**Fluids of light: from hydrodynamics to quantum phase transition**

Under specific conditions, photons could behave as a quantum gas with interaction, we refer this as a "fluid of light". In this talk, we present an experimental platform for fluid of light in a hot Rubidium vapor [1] allowing to model 2D+1 Hamiltonians using all-optical control . Using full-field retrieval of the quantum fluid, we are able to measure momenta distributions and hydrodynamical observables and use this information to probe the superfluid transition [2, 3] in a time-resolved manner. We also engineer the quantum fluid to study the dynamics of quantized vortices and scale it towards the study of turbulence [4]. Finally, we present future direction of the field on quantum phase transition.

[1] Glorieux, Q. et al. Hot atomic vapors for nonlinear and quantum optics. New Journal of Physics 25, 051201 (2023).

[2] Huynh, J. et al. Two-dimensional superflow past an obstacle of arbitrary penetrability: Exact results for the critical velocity 2023. arXiv: 2305.01293.

[3] Michel, C. et al. Superfluid motion and drag-force cancellation in a fluid of light. Nat. Comm. 9, 2108 (2018).

[4] Abobaker, M. et al. Inverse energy cascade in two-dimensional quantum turbulence in a fluid of light 2022. arXiv: 2211.08441t:

The pretalk will be given by Niklas Rasch, KIP, University of Heidelberg

For information about the CQD Colloquium, please see: https://cqd.uni-heidelberg.de/events/cqdcolloquium

Next CQD Colloquium (funded by Structures) will be given by Dr. Giacomo Roati.

Please note the place and time:

**Wednesday, 19.06. at 2.30 p.m., PI, INF 226, K 1-3, Goldenbox**

The main talk will be given by Dr. Giacomo Roati, CNR-INO and LENS, Sesto Fiorentino, Italy about

**Vortex matter in strongly-correlated superfluids**

Topological defects play a crucial role in shaping the properties and structures of various out-of-equilibrium physical and biological systems across a broad spectrum of scales. These systems range from planetary atmospheres and turbulent flows in classical and quantum fluids to the electrical signaling in excitable biological media [1]. In superfluids and superconductors, the motion of quantized vortices is linked to the onset of dissipation, which limits the superflow [2]. Comprehending vortex dynamics poses a significant challenge due to the intricate interplay among vortices, disorder, and system dimensionality.

We tackle this challenge by investigating vortex matter in planar homogeneous Fermi superfluids [3]. By engineering vortex configurations and monitoring their evolution through tracking vortex trajectories, we gain unparalleled control over vortex dynamics. This capability transforms our system into an ideal "quantum laboratory" for unraveling the fundamental nature of vortex-driven instabilities and dissipation [4,5]. Our research opens prospects for understanding vortex-matter phenomena in strongly correlated superfluids.

References

[1] Spiral and Vortices, K. Tsuji and S. C.Müller Editors, Springer Nature (2019) [2] B. I. Halperin, G. Refael and E. Demler, Int. J. Mod. Phys, B 24, 20n21 (2010) [3] W. J. Kwon et al., Nature, 600 (2021)

[4] D. Hernandez-Rajkov et al., Nature Physics (2024)

[5] N. Grani et al., in preparation

The pretalk will be given by Tobias Hammel, PI, University of Heidelberg

For information about the CQD Colloquium, please see: https://cqd.uni-heidelberg.de/events/cqdcolloquium

Kirchhoff's scientific activities were so innovative and groundbreaking that they still serve as the basis for research and industrial applications in physics, chemistry, and electrical engineering today. In honor of the 200th anniversary of Gustav Kirchhoff's birth, the Kirchhoff-Institute for Physics, in collaboration with the Physics Institute and the University Museum, is presenting an exhibition to discover new things and reclassify old ones.

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