  In the Gribov-Zwanziger scenario the confinement of gluons is attributed to
an enhancement of the spectrum of the Faddeev-Popov operator near eigenvalue
zero. This has been observed in functional and also in lattice calculations.
The linear rise of the quark-anti-quark potential and thus quark confinement on
the other hand seems to be connected to topological excitations. To investigate
whether a connection exists between both aspects of confinement, the spectrum
of the Faddeev-Popov operator in two topological background fields is
determined analytically in SU(2) Yang-Mills theory. It is found that a single
instanton, which is likely irrelevant to quark confinement, also sustains only
few additional zero-modes. A center vortex, which is likely important to quark
confinement, is found to contribute much more zero-modes, provided the vortex
is of sufficient flux. Furthermore, the corresponding eigenstates in the vortex
case satisfy one necessary condition for the confinement of quarks.
