  Motivated by chromosomes enclosed in nucleus and the recently discovered
active topological glass, we study a spherically confined melt of long
nonconcatenated active polymer rings. Without activity, the rings exhibit the
same average large-scale conformational properties as chromatin fiber. Upon
activating consecutive monomer segments on the rings, the system arrives at a
glassy steady state due to activity-enhanced topological constraints. The
latter generate coherent motions of the system, however the resulting
large-scale structures are inconsistent with the fractal globule model. We
observe microphase separation between active and passive segments without
systematic trends in the positioning of active domains within the confining
sphere. We find that tank-treading of active segments along the ring contour
enhances active-passive phase separation in the state of active topological
glass when both diffusional and conformational relaxation of the rings are
significantly suppressed. Finally, although the present model of partly-active
rings is not compatible with the large-scale chromatin organization, our
results suggest that the activity-enhanced entanglements that result in
facilitated intra- and inter-chromosomal contacts might be relevant for
chromatin structure at smaller scales.
