  Isogeometric Analysis is a high-order discretization method for boundary
value problems that uses a number of degrees of freedom which is as small as
for a low-order method. Standard isogeometric discretizations require a global
parameterization of the computational domain. In non-trivial cases, the domain
is decomposed into patches having separate parameterizations and separate
discretization spaces. If the discretization spaces agree on the interfaces
between the patches, the coupling can be done in a conforming way. Otherwise,
non-conforming discretizations (utilizing discontinuous Galerkin approaches)
are required. The author and his coworkers have previously introduced multigrid
solvers for Isogeometric Analysis for the conforming case. In the present
paper, these results are extended to the non-conforming case. Moreover, it is
shown that the multigrid solves get even more powerful if the proposed smoother
is combined with a (standard) Gauss-Seidel smoother.
