  Understanding the spatial organisation of the genome in the cell nucleus is
one of the current grand challenges in biophysics. Certain biochemical -- or
epigenetic -- marks that are deposited along the genome are thought to play an
important, yet poorly understood, role in determining genome organisation and
cell identity. The physical principles underlying the interplay between
epigenetic dynamics and genome folding remain elusive. Here we propose and
study a theory that assumes a coupling between epigenetic mark and genome
densities, and which can be applied at the scale of the whole nucleus. We show
that equilibrium models are not compatible with experiments and a qualitative
agreement is recovered by accounting for non-equilibrium processes which can
stabilise microphase separated epigenomic domains. We finally discuss the
potential biophysical origin of these terms.
