Gravitational microlensing as a probe for dark matter clumps
  Extended dark matter (DM) substructures may play the role of microlenses in
the Milky Way and in extragalactic gravitational lens systems (GLSs). We
compare microlensing effects caused by point masses (Schwarzschild lenses) and
extended clumps of matter using a simple model for the lens mapping. A
superposition of the point mass and the extended clump is also considered. For
special choices of the parameters, this model may represent a cusped clump of
cold DM, a cored clump of self-interacting dark matter (SIDM) or an ultra
compact minihalo of DM surrounding a massive point-like object. We built the
resulting micro-amplification curves for various parameters of one clump moving
with respect to the source in order to estimate differences between the light
curves caused by clumps and by point lenses. The results show that it may be
difficult to distinguish between these models. However, some region of the
clump parameters can be restricted by considering the high amplification events
at the present level of photometric accuracy. Then we estimate the statistical
properties of the amplification curves in extragalactic GLSs. For this purpose,
an ensemble of amplification curves is generated yielding the autocorrelation
functions (ACFs) of the curves for different choices of the system parameters.
We find that there can be a significant difference between these ACFs if the
clump size is comparable with typical Einstein radii; as a rule, the
contribution of clumps makes the ACFs less steep.
