
Selfassembly, modularity and physical complexitySebastian E. Ahnert, Iain G. Johnston, Thomas M.A. Fink, Jonathan P.K. Doye and Ard A. LouisPhys. Rev. E. 82, 026117 (2010)AbstractWe present a quantitative measure of physical complexity, based on the amount of information required to build a given physical structure through selfassembly. Our procedure can be adapted to any given geometry, and thus to any given type of physical system. We illustrate our approach using selfassembling polyominoes, and demonstrate the breadth of its potential applications by quantifying the physical complexity of molecules and protein complexes. This measure is particularly well suited for the detection of symmetry and modularity in the underlying structure, and allows for a quantitative definition of structural modularity. Furthermore we use our approach to show that symmetric and modular structures are favoured in biological selfassembly, for example of protein complexes. Lastly, we also introduce the notions of joint, mutual and conditional complexity, which provide a useful distance measure between physical structures.The full paper is available from Phys. Rev. E and arXiv.org. 