A thesis submitted September 2015 for the degree of Doctor of Philosophy and defended November 6, 2015.
The PhD School of Science,
Faculty of Science,
Niels Bohr Institute,
University of Copenhagen
Enforced Scale Selection in Field Theories of Mechanical and Biological Systems
The collective motion of driven or self-propelled interacting units is in many natural systems known to produce complex patterns. This thesis considers two continuum field theories commonly used in describing pattern formation and dynamics: The first one, the phase field crystal model, which describes the dynamical and equilibrium properties of crystalline material, is used to study the coarsening dynamics of polycrystalline materials in two and three dimensions.
A generalization introducing a faster elastic relaxation time scale is then used to study the plastic deformation and dislocation dynamics of single crystals. Secondly, a continuum theory describing mesoscopic turbulence of biological active matter, which is used to study long-range ordered vorticity patterns generated by cell divisions in a endothelial cell layer.