  We investigate the effects of cell division and apopotosis on collective
dynamics in two-dimensional epithelial tissues. Our model includes three key
ingredients observed across many epithelia, namely cell-cell adhesion, cell
death and a cell division process that depends on the surrounding environment.
We show a rich non-equilibrium phase diagram depending on the ratio of cell
death to cell division and on the adhesion strength. For large apopotosis
rates, cells die out and the tissue disintegrates. As the death rate decreases,
however, we show, consecutively, the existence of a gas-like phase, a gel-like
phase, and a dense confluent (tissue) phase. Most striking is the observation
that the tissue is self-melting through its own internal activity, ruling out
the existence of any glassy phase.
