  It is well known that the topology of gauge configurations generated in a
Markov Monte-Carlo chain freezes as the continuum limit is approached. The
corresponding autocorrelation time increases exponentially with the inverse
lattice spacing, affecting the ergodicity of the simulation. In SU(N) gauge
theories for large N this problem sets in at much coarser lattice spacings than
for N=3. This means that its systematics can be studied on lattices that are
smaller in terms of the number of lattice sites. It has been shown that using
open boundary conditions in time allows instantons to be created and destroyed,
restoring topological mobility and ergodicity. However, with open boundary
conditions translational invariance is lost and the influence of spurious
states propagating from the boundary into the bulk on physical correlators
needs to be carefully evaluated. Moreover, while the total topological charge
can be changed, the mobility of instantons across the lattice is still reduced.
We consider SU(7) Yang-Mills theory and analyse its topological content in the
periodic and open boundary condition cases. We also investigate scalar and
pseudo-scalar glueball correlation functions.
