Hamburg 2009 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 33: Quantengase: Bosonen

Q 33.4: Talk

Wednesday, March 4, 2009, 15:15–15:30, VMP 6 HS-A

Casimir energy of a BEC: from moderate interactions to the ideal gas — •Jürgen Schiefele and Carsten Henkel — Universität Potsdam, Institut für Physik und Astronomie, Karl-Liebknecht-Str. 24/25, 14 476 Potsdam, Germany

A pair of parallel conducting plates separated by vacuum imposes boundary conditions on the electromagnetic vacuum fluctuations. This causes a change in the (infinite) vacuum energy density, and leads to an attractive interaction between the two plates. The resulting force on the plates is known as the Casimir force.

When a weakly interacting dilute Bose-Einstein condensate (BEC) is confined between parallel plates, there is an analogous effect caused by the quantum fluctuations (Bogoliubov modes) on top of the ground state of the BEC. We derive a renormalized expression for the zero temperature Casimir energy of a BEC confined to a parallel plate geometry with periodic boundary conditions. Our expression is formally equivalent to the free energy of a bosonic field at finite temperature, with a nontrivial density of modes that we compute analytically. As a function of the interaction strength, it smoothly describes the transition from the weakly interacting Bogoliubov regime (phononic Casimir effect) to the non-interacting ideal BEC (no Casimir effect).

J. Schiefele and C. Henkel, J. Phys A (2009) in press.