Smooth Teeth: Why Multipoles Are Perfect Gears

Smooth Teeth: Why Multipoles Are Perfect Gears.
Johannes Schönke
Phys. Rev. Applied 4, 064007 (2015)

Definition of the angles which describe the rotation of the dipoles (red). The upper panel introduces the two angles θ and φ which set the positions of the rotation axes (light gray). The rotation axes are restricted to lie in the x−y plane. The angles θ and φ (and, therefore, the rotations axes) are fixed for a given configuration. The lower panel introduces the angles α and β which correspond to the 2 degrees of freedom the system possesses. α and β describe the actual orientation of the two dipoles during rotation.