Se p 20 04 Conformally invariant energies of knots II ∗

Conformally invariant functionals on the space of knots are introduced via extrinsic confor-mal geometry of the knot and integral geometry on the space of spheres. Our functionals are expressed in terms of a complex-valued 2-form which can be considered as the cross-ratio of a pair of infinitesimal segments of the knot. We show that our functionals detect the unknot as the total curvature does, and that their values explode if a knot degenerates to a singular knot with double points.