Description
Viro's writhe is an invariant of rigid isotopy for real algebraic curves in projective three-space. We show that it agrees with the topological degree of a natural map from a certain projective bundle over the second symmetric product of the curve to projective three-space. This map admits a relative Ulrich line bundle. The space of global sections of this line bundle carries a symmetric bilinear form in a natural way. The signature of this bilinear form again agrees with Viro's writhe. This is a joint work in progress with Daniele Agostini.
