Jason Parsley
Department of Mathematics, University of Georgia, Athens, GA 30605
Biot-Savart operator, helicity, and linking on
S3
We extend the Biot-Savart law from physics to an operator BS
acting on all vector fields on S3, a geometric
setting for electrodynamics in positive curvature. We show that Maxwells
equations hold and that BS acts as a right inverse to curl. We
then discuss its application to energy-minimization problems in geometry and
physics that depend on curl eigenvalues. Also, BS allows us to
construct linking integrals on S3. As one further
application, we can express the helicity of a vector field, a measure of how
much it coils around itself, as
H(V) = <V, BS(V)>. We
find upper bounds for helicity on the three-sphere; our bounds are not sharp
but within an order of magnitude.