Robert Weis

Kirchhoff Institute for Physics

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.

Ruperto Carola Lecture Series 200 Years Gustav Kirchhoff

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.

Physikalisches Kolloquium

10. April 2025 5:30 pm  Tipping phenomena in the climate system

Prof. Dr. Henk Dijkstra, Physical Oceanography, University of Utrecht, more...

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Special CQD Seminar given by Felix Werner,College de France, Monday, the 10th of February, 16:30 p.m.,Goldbox

Next CQD special seminar will be given by Felix Werner, Laboratoire Kastler Brossel, Ecole Normale Superieure & College de France

 

Please note the place and time: Monday, the 10th of February, 16:30 p.m., PI, INF 226, K 1-3, Goldbox

 

The seminar will be about: Three-body contact for fermions

Felix Werner, Laboratoire Kastler Brossel, Ecole Normale Superieure & College de France

 

The resonant Fermi gas, i.e. two-component fermions in 3D interacting by a short-range

potential of large scattering length a2 , is a textbook model describing cold atoms near

a Feshbach resonance.

A key quantity is the 2-body contact C2 , which determines e.g. the number of nearby

fermion pairs, the tail of the single-particle momentum distribution, the derivative of the

energy with respect to a2 , or the 2-body loss rate [1,2] .

Based on the non-trivial power-law scaling of the 3-body wavefunction at short distances,

we introduce the three-body contact C3 , in terms of which we express e.g. the number

of nearby fermion triplets, or the large-momentum tail of the two-particle momentum

distribution. The formation rate of deeply bound dimers by three-body recombination is

expressed in terms of C3 and a parameter a3 defined through the asymptotic behavior

of the zero-energy 3-body wavefunction at distances between the range and |a2| [3].

We compute C3 to leading order in the non-degenerate limit for the homogeneous gas,

using the exact 3-body wavefunction at the unitary limit a2 = ∞, and a diagrammatic

approach at negative a2 . In the Feynman diagram technique, the three-body shortdistance

power-law scaling comes from a large-wavevector tail of the 3-body T-matrix [4].

It is an open challenge to measure C3 and a3 experimentally, and to compute C3 in the

degenerate regime.

 

[1] S. Tan, Ann. Phys. 323, 2952 (2008); ibid. 323, 2971 (2008)

[2] E. Braaten and L. Platter, Phys. Rev. Lett. 100, 205301 (2008)

[3] F. Werner and X. Leyronas, Comptes Rendus Physique 25, 179 (2024)

[4] X. Leyronas and F. Werner, in preparation


 

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