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S. Manz, R. Bücker, Th. Betz, C. Koller, S. Hofferberth, I. Mazets, A. Imambekov, E. Demler, A. Perrin, H.-J. Schmiedmayer, Thorsten Schumm:
"Two-point density correlations of quasicondensates in free expansion";
Physical Review A, 81 (2010), 031610-1 - 031610-4.

We measure the two-point density correlation function of freely expanding quasicondensates in the weakly
interacting quasi-one-dimensional (1D) regime. While initially suppressed in the trap, density fluctuations emerge
gradually during expansion as a result of initial phase fluctuations present in the trapped quasicondensate.
Asymptotically, they are governed by the thermal coherence length of the system. Our measurements take place
in an intermediate regime where density correlations are related to near-field diffraction effects and anomalous
correlations play an important role. Comparison with a recent theoretical approach described by Imambekov
et al. yields good agreement with our experimental results and shows that density correlations can be used for
thermometry of quasicondensates.

http://dx.doi.org/10.1103/PhysRevA.81.031610

http://publik.tuwien.ac.at/files/PubDat_185542.pdf