We analyze coherence effects during the splitting of a quasi one-dimensional
condensate into two spatially separated ones and their subsequent merging into
a single condensate. Our analysis takes into account finite-temperature
effects, where phase fluctuations play an important role. We show that, at
zero-temperature, the two split condensates can be merged into a single one
with a negligible phase difference. By increasing temperature to a finite value
below the critical point for condensation (Tc), i.e., 0≤T/Tc<1, a
considerable enhancement of phase and density fluctuations appears during the
process of splitting and merging. Our results show that if the process of
splitting and merging is sufficiently adiabatic, the whole process is quite
insensitive to phase fluctuations and even at high temperatures, a single
condensate can be produced.Comment: 8 pages, 6 figure