Hannover 2020 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 49: Quantum gases (Miscellaneous)

Q 49.1: Hauptvortrag

Donnerstag, 12. März 2020, 14:00–14:30, e214

New physical concepts: Fermionic Exchange Force and Bose-Einstein Force — •Christian Schilling — Arnold Sommerfeld Center for Theoretical Physics, LMU München

The particle-exchange symmetry has a strong influence on the behavior and the properties of systems of N identical particles. While fermionic occupation numbers are restricted according to Pauli’s exclusion principle, 0 ≤ nk≤ 1, bosonic occupation numbers can take arbitrary values 0 ≤ nkN. It is also a matter of fact, however, that occupation numbers in realistic systems of interacting fermions and bosons can never attain the maximal possible value, i.e., 1 and N, respectively. By resorting to one-particle reduced density matrix functional theory we provide an explanation for this: The gradient of the exact functional diverges repulsively whenever an occupation number nk tends to attain the maximal value. In that sense we provide in particular a fundamental and quantitative explanation for the absence of complete Bose-Einstein condensation (as characterized by nk=N) in nature. These new concepts are universal in the sense that the fermionic exchange force and the Bose-Einstein force are present in all systems regardless of the particle number N, the spatial dimensionality and the interaction potentials.

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