Cold atoms Lecture 4. 1^st November, 2006 Interacting bosons in the trap Are the interactions important? Fortunate properties of the interactions Fortunate properties of the interactions Interatomic interactions Interatomic interactions Interatomic interactions Scattering length, pseudopotential Experimental data Many-body Hamiltonian Gross-Pitaevskii equation at zero temperature Gross-Pitaevskii equation Gross-Pitaevskii equation Gross-Pitaevskii equation Gross-Pitaevskii equation – variational interpretation Gross-Pitaevskii equation – variational interpretation Gross-Pitaevskii equation – variational interpretation Gross-Pitaevskii equation – variational interpretation Interacting atoms in a parabolic trap Importance of the interaction Importance of the interaction Importance of the interaction Importance of the interaction Importance of the interaction The end On the way to the mean-field Hamiltonian On the way to the mean-field Hamiltonian On the way to the mean-field Hamiltonian On the way to the mean-field Hamiltonian Variational approach to the condensate ground state Variational estimate of the condensate properties Variational estimate of the condensate properties Variational estimate of the condensate properties Variational estimate of the condensate properties Variational estimate of the condensate properties Variational estimate of the condensate properties Variational estimate of the condensate properties