A formula governing the evolution of twist in moving filaments or ribbons of finite extent is derived. This evolution is shown to be made up of a 'dynamic' part corresponding to physical properties of the filament or ribbon and a 'geometric' part due to the motion of the filament or ribbon core itself. These results are used to extend classical elastic rod theory to the case of motion including dynamically evolving twist. In addition, the averaged geometric contribution is noted to be minus the time rate of change of the writhing number and it is shown that the writhe is a conserved quantity for closed filaments moving according to certain integrable curve dynamics.
ASJC Scopus subject areas
- Statistical and Nonlinear Physics
- Mathematical Physics
- General Physics and Astronomy