Debris disks are dusty and/or gasous disk that are viewed in scattered
light and thermal emission around stars around 107–108 yr.
It is well known that the dust in these system is not primodial. It is
short lived and must be continuously replenished by colliding
planetesimals. Most of them appear distorted by the gravitational
pertubations by inner planets or stellar companions. This is why these
systems are viewed today as young planetary systems.
Debris disks are collisional systems. Thanks to collisional cascade
towards smaller size, the dust particles are transported outwards by
radiation or stellar wind pressure. Below a given blow-off size they
escape the system. This model explains the radial density profiles observed.
The various asymmetries, clumps and other dynamical structures such as spiral arms are though to originate in gravitational perturbations
by planets and/or companions. Planets usually create gaps in disks,
but they also sculpt disks via their mean-motion resonances. Clumpy
structures are often invoked as resulting from such an interaction.
Stellar companions usually truncate the disk, sometimes confining them
to thin annular structures. They also help creating spiral patterns,
either tidally or by secular interaction. In this context, the
situation is different whether the perturbing companions are bound or
just passing stars. In any case, dynamical studies (often specific to
each system) can greatly help constraining the configuration and the
past history of these systems.