In a recent talk about physics and mechanics inside the cell, I heard such terms as 'force monopole' and 'force dipole'. What do such terms mean?
Are they talking about the angular distributions, viz. the $\ell=0,1,...$ modes of the spherical harmonics? If so, then what would a force monopole, dipole, etc. look like?
Any references on this topic? A simple search did not turn up anything.