Robert Weis

Kirchhoff-Institut für Physik

Das Kirchhoff-Institut für Physik (KIP) trägt den Namen eines herausragenden Physikers des 19. Jahrhunderts: Gustav Robert Kirchhoff, der 21 Jahre in Heidelberg wirkte. Seine weithin berühmten Vorlesungen über experimentelle und theoretische Physik zogen viele Studenten hierher. Kirchhoffs theoretische und experimentelle Forschungen sind außerordentlich vielseitig, sie umfassen elektrische, magnetische, optische, elastische, hydrodynamische und thermische Vorgänge. Allgemein bekannt sind seine Gesetze zur Verzweigung von Strömen. In die Heidelberger Zeit fällt die Entdeckung der Spektralanalyse zusammen mit Robert Wilhelm Bunsen und deren Anwendung auf die Sonnenstrahlung, mit der Kirchhoff die Astrophysik begründete, sowie die Formulierung des Strahlungsgesetzes, das zum Tor für die Quantenphysik wurde. Dieser Vielseitigkeit fühlt sich das KIP verpflichtet.

Physikalisches Kolloquium

2. Dezember 2022 17:00 Uhr  Folding the World: Infinite growth on a finite planet

Prof. Anders Levermann, Ph.D., Potsdam-Institut für Klimafolgenforschung, mehr...

Aktuelle Mitteilungen

Special CQD (funded by STRUCTURES), November 29, 2022, 2 p.m., KIP, SR 1.404

Dr. I-Kang Liu, Newcastle University, about:

Coherent and incoherent structures in fuzzy dark matter halos

 

Dark matter(DM) halos composed of ultralight bosons exhibit wavy behaviour with de Broglie wavelengthin cosmological scales, known as fuzzy DM (FDM), wave DM or BECDM. To the leading order of the space-time metric, the effective equation of motion is the Schrodinger-Poison system of equation, a classical-field wavefunction coupled to Newtonian gravity, and is reminiscentof the universal phenomenon of Bose-Einstein condensation(BEC), described by a macroscopic condensate wavefunction.

This model reproduces the density distribution in large length scales in the cold DM model, called Navarro–Frenk–White profile, and can be a candidate to resolve the missing-satellite, too-big-to-fail and cusp-core problems with a compact solitonic core in the centre of a halo. Here inspired by widely-studied laboratory atomic systems we systematically examine the BEC concept by examining the field fluctuations in fuzzy dark matter halos, generated by our merger simulations, via probing the spatial phase-phase and density-density correlation functions to unveil the FDM halo properties. We find out that the solitonic core is fully coherent and coincides with the Penrose-Onsager condensate mode, exhibiting off-diagonal-long-range order, of a virialized halo. Moving outward from the core, fluctuations enhance and the bimodal fit of the core-halo profile can nicely capture the crossover length scale. By looking at the energy distribution, we demonstrate that these fluctuations are mainly sourced by a large number of quantized vortices, indicating a turbulence-like state, which is persistent in our simulation. In addition, the intervortex distance scale matches the granule one by comparing the vortex energy and overdensity power spectra. This work provides a new picture to investigate the FDM halos.

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Special CQD Seminar (funded by STRUCTURES) , November 30, 2022, 5 p.m., KIP, INF 227, Hörsaal 2

Dr. Christian Ott, Max-Planck-Institut für Kernphysik, Heidelberg, about:

Site-specific and state-resolved coherent quantum control of atoms and molecules

 

Using intense ultrashort laser pulses with a duration across the femtosecond and attosecond timescale, it is possible to couple and control multi-electron transitions which involve short-lived states in atoms and molecules. Their extreme-ultraviolet (XUV) and x-ray absorption spectra hereby encode the time-resolved dynamics with state-specific spectroscopic information about the relevant quantum states. In this talk, I will first provide an overview how we extract quantum-dynamics information from spectral absorption line shapes. We will discuss for instance the laser-controlled transformation of Fano to Lorentzian spectral line shapes of a correlated two-electron transition in helium, and how its absorption profile coherently builds up on the femtosecond timescale. We will further apply these concepts to nonlinear absorption spectroscopy with free-electron lasers and discuss XUV-induced energy shifts of strongly coupled states, e.g., in helium and neon atoms. Finally, we will also look at time-resolved measurements with XUV-pump – XUV-probe absorption spectroscopy to resolve the state-specific dynamics in small molecules, accessing structural dynamics from the perspective of individual electronic states. With all these experiments, we explore new methods of nonlinear light-matter interaction for the quantum control of atoms and molecules down to the natural attosecond timescale of the electron motion and coherently addressing specific transitions of individual constituents within the larger quantum system.

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Kirchhoff-Institut für Physik
Im Neuenheimer Feld 227
D-69120 Heidelberg

Tel.: 06221 - 54-9100
info@kip.uni-heidelberg.de
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