Symmetry breaking is a central organizing principle in morphogenesis, underlying phenomena ranging from cell polarization and tissue patterning to asymmetric cell division. In this talk, I will discuss how spontaneous symmetry breaking can emerge from the nonlinear coupling of geometry, hydrodynamic flows, and active stresses in deformable active surfaces.

The talk is divided into two parts. In the first part, I consider active fluid surfaces in free space. Using a hydrodynamic theory and variational framework for active surfaces, I will show that increasing activity can destabilize a spherical surface through a spontaneous polarization instability, leading to self-organized accumulation of motors at one pole and symmetry-broken surface geometries [1]. I will then show how division-like behavior can instead be generated by imposing an inhomogeneous recruitment of motors toward the equator, which stabilizes symmetric constriction and produces active surface division as a self-organized shape transition [1]. In the second part, I will discuss how confinement qualitatively reshapes this behavior. Remarkably, as confinement is tightened, a symmetrically dividing active surface that is stable in free space can itself become unstable, undergoing a confinement-induced symmetry-breaking transition in which polarized geometries emerge through bifurcations in the stationary shape space. This reveals confinement as a control parameter capable of redirecting active stresses and selecting new symmetry-broken states [2].  Taken together, these results suggest symmetry breaking can arise both spontaneously from activity and be induced geometrically through confinement.

[1] D. Gao, H. Sun, R. Ma, and A. Mietke, Self-organized dynamics and emergent shape spaces of active isotropic fluid surfaces, Phys. Rev. Res. 8, 023046 (2026).

[2] D. Gao, A. Mietke, and R. Ma, Confinement-Induced Symmetry Breaking of Active Surfaces, arXiv:2602.21519.

Biography

Rui Ma is an Associate Professor at Xiamen University working in theoretical biophysics. He received his Ph.D. from Tsinghua University, conducted research at MPI-PKS in Germany, and was a postdoctoral researcher at Yale University before joining Xiamen University in 2020 as a Nanqiang Scholar. His research focuses on membrane mechanics, active surfaces, and the physics of morphogenesis.

Inviter: Zhong-Can Ou-Yang