A4: Multiscale rheological inverse problems and active processes in cells

Lead PI: Anne Wald
Collaborating PIs: Andreas Janshoff, Sarah Köster, Tim Salditt, Peter Sollich
Overarching research question: How can rheological data for active matter be evaluated in a stable way with respect to noise?

The determination of mechanical properties, such as the viscosity, of active matter usually requires the evaluation of indirect measurement data, since the respective parameters cannot be determined directly. Mathematically, such problems are called inverse problems: we want to reconstruct an unknown quantity from its impact on an observable quantity, where the measurements are usually noisy. The goal of this project is to formulate, analyze and solve inverse problems arising in rheological experiments on multiple scales. The experiments conducted in project A6 serve as a main application: Observations of the flow field inside actomyosin droplets caused by the interacting proteins are used to determine their cause, summarized as an active force density, along with a potentially heterogeneous viscosity. For a more efficient solution of this problem, we aim at exploiting microrheological measurements and integrate the research from other projects (A5, A7, B2) in the modelling process.

Core field: theoretical physics/mathematics

PhD training objectives: inverse problems in cell physics (ill-posedness, regularization techniques); modelling (rheology, active processes); understanding of the data generation process and experimental techniques; implementation of algorithms.