  We investigate specific models for a dark energy universe leading to
Quasi-Rip and Pseudo-Rip cosmologies. In the Quasi-Rip model the equation of
state parameter w is less than -1 in the first stage, but becomes larger than
-1 in the second stage. In the Pseudo-Rip model the Hubble parameter tends to a
constant value in the remote future, although w is always less than -1.
Conditions for the appearance of the Quasi-Rip and the Pseudo-Rip in terms of
the parameters in the equation of state are determined. Analogies with the
theory of viscous cosmology are discussed.
