  A living cell is an active environment where the organization and dynamics of
chromatin are affected by different forms of activity. Optical experiments
report that loci show subdiffusive dynamics and the chromatin fiber is seen to
be coherent over micrometer-scale regions. Using a bead-spring polymer chain
with dipolar active forces, we study how the subdiffusive motion of the loci
generate large-scale coherent motion of the chromatin. We show that in the
presence of extensile (contractile) activity, the dynamics of loci grows faster
(slower) and the spatial correlation length increases (decreases) compared to
the case with no dipolar forces. Hence, both the dipolar active forces modify
the elasticity of the chain. Interestingly in our model, the dynamics and
organization of such dipolar active chains largely differ from the passive
chain with renormalized elasticity.
