# Dresden 2009 – wissenschaftliches Programm

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# DY: Fachverband Dynamik und Statistische Physik

## DY 12: Poster I

### DY 12.47: Poster

### Dienstag, 24. März 2009, 14:30–16:30, P1A

**Bose condensation for attractive interaction?** — •Michael Männel^{1}, Pavel Lipavský^{2,3}, Klaus Morawetz^{4,5}, and Michael Schreiber^{1} — ^{1}Institute of Physics, Chemnitz University of Technology, 09107 Chemnitz, Germany — ^{2}Institute of Physics, Academy of Sciences, Cukrovarnická 10, 16253 Prague 6, Czech Republic — ^{3}Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 12116 Prague 2, Czech Republic — ^{4}Research-Center Dresden-Rossendorf, Bautzner Landstr. 128, 01328 Dresden, Germany — ^{5}International Center of Condensed Matter Physics, University of Brasilia, 70904-970, Brasilia-DF, Brazil

We investigate a Bose gas with finite range interaction using a scheme to eliminate successive collisions as well as a single-channel T-matrix approximation. For attractive interaction we find a Evans-Rashid transition from a quasi-ideal Bose gas to a BCS like phase with a gaped dispersion. The gap decreases with increasing density. At another critical point the gap vanishes, the dispersion becomes linear for small momenta and a Bose condensate appears. It is well known, that a Bose gas with contact interaction and a negative scattering length becomes instable and undergoes a gas-liquid or gas-solid transition. Looking for this instability we also calculate the pressure for the three phases.