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  • Letter
  • Open Access

Geometry of T1 transitions in epithelia

Pierre A. Haas*

  • *Contact author: haas@pks.mpg.de
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Phys. Rev. E 112, L042401 – Published 9 October, 2025

DOI: https://doi.org/10.1103/kdnb-bxdx

Abstract

The flows of tissues of epithelial cells often involve T1 transitions. These neighbor exchanges are irreversible rearrangements crossing an energy barrier. Here, by an exact geometric construction, I determine this energy barrier for general, isolated T1 transitions dominated by line tensions. I show how deviations from regular cell packing reduce this energy barrier, but find that line tension fluctuations increase it on average. By another exact construction, I prove that the nonlinear tensions in vertex models of tissues also resist T1 transitions. My results thus form the basis for coarse-grained understanding of cell neighbor exchanges for continuum descriptions of epithelia.

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Phys. Rev. E 112, L042401– Published 9 October, 2025
  • Received 23 April 2025
  • Accepted 11 September 2025
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