2005/05/16 by S. J. Han, Han, S. J.
Physics and Astronomy · #FOS: Physical sciences #Other Condensed Matter (cond-mat.other) #cond-mat.other
paper · pdf · doi:10.48550/arxiv.cond-mat/0505372
total 16 pages, including 1 figure
arxiv created 2005/09/14 · arxiv updated 2009/12/01
A theory of collective excitations in Bose-Einstein condensation in a trap is developed based on the quantum Hamilton-Jacobi equation of Bohm and the phase coherence along with the idea of off-diagonal long range order of Penrose and Onsager. First, we show that a free surface behaves like a normal fluid - a breakdown of superfluidity. Second, inside the free surface it is shown that the spectrum of phonons is of the form ω=ck scaled with the external potential, where the speed of (first) sound, c=[4πaρℏ2]1/2/M and k is the wave number. Third, in the limit a→ 0, the hard spheres in the Bose-Einstein condensation collapse to a close-packed classical lattice with the zero-point vibrational motion about fixed points.