The dynamics of coherence between coupled and decoupled one-dimensional quasicondensates

We reproduce the sub-exponential decoherence of one-dimensional quasicondensates observed in recent experiments. Counter-intuitively, the quasicondensates may decohere even when stongly coupled, if the temperature is large enough or the peak density is low enough to allow significant density fluctuations. We also propose an experiment to investigate the growth of coherence between two initially incoherent quasicondensates. We predict that the coherence will rise on a much slower timescale, and the final coherence again depends strongly on the density fluctuations.