  The secular instability and nonlinear evolution of the m=2 f-mode (bar-mode)
driven by gravitational radiation reaction in a rapidly rotating, newly formed
neutron star are reviewed. There are two types of rotating bars which generate
quite different gravitational waveforms: those with large internal rotation
relative to the bar figure (Dedekind-like bars) have GW frequency sweeping
downward during the evolution, and those with small internal rotation
(Jacobi-like) have GW frequency sweeping upward. Various sources of viscosity
(which affects the instability) in hot nuclear matter are reexamined, and the
possible effect of star-disk coupling on the bar-mode instability is also
discussed.
