  Within the context of epithelial monolayers, T1 transitions, also known as
cell-intercalations, are topological rearrangements of cells that contribute to
fluidity of the epithelial monolayers. We use a multi-phase field model to show
that the ensemble-averaged flow profile of a T1 transition exhibits a saddle
point structure, where large velocities are localised near cells undergoing T1
transitions, contributing to vortical flow. This tissue fluidisation
corresponds to the dispersion of cells relative to each other. While the
temporal evolution of the mean pair-separation distance between initially
neighbouring cells depends on specific model details, the mean pair-separation
distance increases linearly with the number of T1 transitions, in a way that is
robust to model parameters.
