  We investigate the ejection dynamics of a ring polymer out of a cylindrical
nanochannel using both theoretical analysis and three dimensional Langevin
dynamics simulations. The ejection dynamics for ring polymers shows two regimes
like for linear polymers, depending on the relative length of the chain
compared with the channel. For long chains with length $N$ larger than the
critical chain length $N_{c}$, at which the chain just fully occupies the
nanochannel, the ejection for ring polymers is faster compared with linear
chains of identical length due to a larger entropic pulling force; while for
short chains ($N<N_c$), it takes longer time for ring polymers to eject out of
the channel due to a longer distance to be diffused to reach the exit of the
channel before experiencing the entropic pulling force. These results can help
understand many biological processes, such as bacterial chromosome segregation.
