TY  - JOUR
A1  - Öhberg, P.
A1  - Surkov, E. L.
A1  - Tittonen, I.
A1  - Stenholm, Stig
A1  - Wilkens, Martin
A1  - Shlyapnikov, G. V.
T1  - Low-energy elementary excitations of a trapped Bose-condensed gas
N2  - We develop a method of finding analytical sotutions of the Bogolyubov-de Gennes equations for the excitations of a Bose condensate in the Thomas-Fermi regime in harmonic traps of any asymmetry and introduce a classification of eigenstates. In the case of cylindrical symmetry we emphasize the presence of an accidental degeneracy in the excitation spectrum at certain values of the projection of orbital angular momentum on the symmetry axis and discuss possible consequences of the degeneracy in the context of new signatures of Bose- Einstein condensation
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Stenholm, Stig
A1  - Wilkens, Martin
T1  - Jumps in quantum theory
N2  - In this paper we review the discussion about quantum jumps. We sketch the historical background before we present the recent revival of this problem originating in the field of atomic investigations. We present both the theoretical methods and their motivations, the relevance to experiments and an attempt at a preliminary discussion of the role of these developments in our fundamental understanding of quantum physics.
Y1  - 1997
ER  -