## Daniel Pearce

I am a theoretical physicist working on the interplay between active matter, geometry and topology. I earned my PhD in 2014 with Prof. Matthew Turner at the University of Warwick working on agent-based models of swarming. My first postdoctoral position was at Leiden University working with Prof. Luca Giomi on a variety of soft matter and active matter physics projects. My second postdoctoral position was at the University of Geneva in the group of Prof. Karsten Kruse. There I applied the physics of active matter to understanding a number of processes within living organisms. During 2021 I was a visiting fellow at MIT Mathematics department and in 2023 I start my own group funded by an SNSF starting grant.

Tuesday April 18th

### Controlling active matter with geometry and topology

Active matter is the study of materials that are able to move themselves, for example as locomotion or changing their shape. During this talk I will discuss how we can take advantage of the interplay between topological defects, geometry and topology to exercise control over active materials. By studying active nematic fluids on a curved surface, we can influence the position and orientation of topological defects according to their charge. This means specific nematic textures can be generated. By studying active contractile actomyosin gels, it is possible to show that only active topological defects with charge +1 can generate curvature, and the sign is related to the phase of the defect. This frees the process from the constraints of the Poincare-Hopf theorem and allows complex surfaces to be generated. This is demonstrated by recreating the shape of a freshwater hydra from the positions of the topological defects. Finally, I will show how these ideas can be applied in the design of new active, nematic solid materials with potential functionality.