  Using analytic stability criteria, we demonstrate that, due to their low
surface mass density and large dark matter content, LSB disks are quite stable
against the growth of global nonaxisymmetric modes such as bars. However,
depending on their (poorly constrained) stellar velocity dispersions, they may
be only marginally stable against local instabilities. We simulate a collision
between an LSB and HSB galaxy and find that, while the HSB galaxy forms a
strong bar, the response of the LSB disk is milder, manifesting weaker rings
and spiral features. The lack of sufficient disk self-gravity to amplify
dynamical instabilities naturally explains the rarity of bars in LSB disks. The
stability of LSB disks may also inhibit interaction-driven gas inflow and
starburst activity in these galaxies.
