  We study an ultracold Bose gas in an optical dipole trap consisting of one
single focused laser beam. An analytical expression for the corresponding
density of states beyond the usual harmonic approximation is obtained. We are
thus able to discuss the existence of a critical temperature for Bose-Einstein
condensation and find that the phase transition must be enabled by a cutoff
near the threshold. Moreover, we study the dynamics of evaporative cooling and
observe significant deviations from the findings for the well-established
harmonic approximation. Furthermore, we investigate Bose-Einstein condensates
in such a trap in Thomas-Fermi approximation and determine analytical
expressions for chemical potential, internal energy and Thomas-Fermi radii
beyond the usual harmonic approximation.
