Alberto Raiola — University of Padua #
Dilution controls phase transitions and memory in epigenetic polymers #
Understanding how epigenetic patterns are established and maintained in living cells, and how these couple to 3D chromatin organisation, is a central open problem in biophysics. Here we introduce diluted chromatin-like magnetic polymer models in which only a fraction of monomers can carry epigenetic marks, while the remaining ones are neutral. This minimal polymer model captures the finite availability of epigenetic modifiers, and moves the system beyond an Ising description toward a different universality class. By combining mean-field theory and simulations, we show that dilution enables epigenetic phase separation, providing a robust physical pathway to first order transitions, which create epigenetic memory through metastability and phase coexistence. Epigenetic memory decays as a stretched exponential, revealing the coexistence of distinct timescales associated with mark spreading and chromatin dynamics. Our results highlight dilution as a key control parameter governing both the phase behavior and the memory capacity of epigenetic polymers.